GIFT  OF 
W  B.   RISING- 


Y'V 


2 


* 

T 


PRINCIPLES 


CHEMICAL    PHILOSOPHY, 


JOSIAH  P.  COOKE,  JR., 


AXD  XDXBJLL06T  0  ILLET.LD 


THIRD  EDITION, 

BEVI5ED    AND    COBEECTED, 


BOSTON: 
JOHX    ALLYX.    PUBLISHER, 

LATE  SEVER,    FRANCIS,    A  CO. 

1874. 


Entered  according  to  Act  of  Congress,  in  the  year  1871,  by 

JOS1AH   P.    COOKE,   JR., 
in  the  Clerk's  Office  of  the  District  Court  of  the  District  of  Massachusetts. 


CAMBRIDGE  : 
PRE88WOBK  BY  JOHN   WILSON  AND  SON. 


PREFACE 

TO  THE   SECOND  EDITION. 


THE  object  of  the  author  in  this  book  is  to  present  the  phi- 
losophy of  chemistry  in  such  a  form  that  it  can  be  made  with 
profit  the  subject  of  college  recitations,  and  furnish  the  teacher 
with  the  means  of  testing  the  student's  faithfulness  and  ability. 
With  this  view  the  subject  has  been  developed  in  a  logical 
order,  and  the  principles  of  the  science  are  taught  indepen- 
dently of  the  experimental  evidence  on  which  they  rest.  It 
is  assumed  that  the  student  has  already  been  made  familiar 
with  this  evidence,  and  with  the  more  elementary  facts  which 
the  philosophy  of  the  science  attempts  to  interpret.  At  most 
of  our  American  colleges  this  instruction  is  given  in  a  course 
of  experimental  lectures  ;  but  for  less  mature  students  a  course 
of  manipulation  in  the  laboratory  will  be  found  a  far  more  effi- 
cient mode  of  teaching,  and  some  preliminary  training  of  this 
kind  ought  to  be  made  one  of  the  requisites  for  admission  to 
our  higher  institutions  of  learning.1  The  author  has  found  by 
long  experience  that  a  recitation  on  mere  facts,  or  descriptions 
of  apparatus  and  experiments,  is  to  the  great  mass  of  college 
undergraduates  all  but  worthless,  while  the  study  of  the  phi- 
losophy of  chemistry  may  be  made  highly  profitable  both  for 
instruction  and  discipline.  It  must  never  be  forgotten,  how- 
ever, that  chemistry  is  peculiarly  an  experimental  science,  and 
that  the  chief  value  of  its  culture  in  a  college  course  depends 
on  the  facilities  which  it  affords  for  cultivating  the  power  of 
observation,  and  for  teaching  the  methods  of  experimental  in- 

l  For  such  a  course  of  practical  study  the  student  can  desire  no  better  guide 
than  the  excellent  work  of  Professors  Eliot  and  Storer,  recently  published, 
"  A  Manual  of  Inorganic  Chemistry,  arranged  to  facilitate  the  Experimental 
Demonstration  of  the  Facts  and  Principles  of  the  Science."  By  C.  W.  Eliot 
and  F.  H.  Storer.  New  York,  1868. 

237516 


iv  PREFACE. 

vestigation.  It  is  not  to  be  expected  or  desired  that  many  of 
our  college  graduates  should  become  professional  chemists,  but 
it  is  all  important  that  every  man  of  culture  should  understand 
or  at  least  appreciate  the  methods  and  the  inductive  logic  of 
physical  science.  The  elementary  facts  of  chemistry  can  be 
efficiently  taught  only  by  leading  the  student  to  observe  for 
himself  the  phenomena  in  which  they  appear,  and  the  attempt 
to  learn  them  memoriter  from  a  text-book  will  not  only  fail  in 
its  immediate  object,  but  miss  the  chief  end  of  scientific  study. 
The  author,  therefore,  would  most  earnestly  deprecate  the  use 
of  this  book  except  as  supplementary  to  some  course  of  labora- 
tory or  lecture-room  instruction.  It  is  only  after  the  student 
has  become,  in  some  limited  measure  at  least,  familiar  with 
chemical  phenomena,  that  he  is  prepared  to  study  the  science 
in  a  systematic  way ;  but  all  who  have  this  preparation  will 
acquire  most  rapidly  a  general  knowledge  of  the  whole  field 
when  the  subject  is  presented  in  a  condensed  and  deductive 
form.  The  author  has  had  especially  in  view  this  class  of  stu- 
dents, and  has  endeavored  to  meet  their  wants. 

Part  I.  of  the  book  contains  a  statement  of  the  general  laws 
and  theories  of  chemistry,  an  explanation  of  its  nomenclature 
and  mode  of  symbolical  notation,  together  with  so  much  of  the 
principles  of  molecular  physics  as  are  constantly  applied  in 
chemical  investigations.  It  might  be  figuratively  called  a 
grammar  of  the  science.  It  is  intended  to  be  studied  inde- 
pendently in  consecutive  lessons,  and  is  adapted  for  class-room 
recitations,  which  should  be  accompanied,  however,  by  such 
experiments  or  further  explanations  as  the  teacher  may  find 
necessary  to  render  the  subject  intelligible. 

Part  II.  of  the  book  presents  the  scheme  of  the  chemical 
elements.  It  should  only  be  studied  in  connection  with  exper- 
imental lectures  or  laboratory  work,  and  will  be  found  chiefly 
usefnl  for  systematizing  and  reviewing  the  facts  and  phenomena 
observed  in  the  lecture-room  or  laboratory.  It  is  in  fact  a  note- 
book intended  to  aid  the  student  in  gaining  the  greatest  benefit 
from  a  course  of  systematic  lectures,  enabling  him  to  insure 
the  accuracy  of  his  knowledge,  and  giving  the  teacher  the 
means  of  testing  the  student's  acquirements. 

The  value  of  problems  as  means  of  culture  and  tests  of  at- 
tainment can  hardly  be  overestimated,  and  they  have  therefore 


PREFACE.  V 

been  made  a  chief  feature  in  this  book.  Since  those  which 
are  here  given  are  chiefly  intended  as  guides  to  the  student, 
the  answers  have  always  been  added ;  and  where  the  method 
was  not  obvious,  the  chief  steps  in  the  solution  have  been  given 
as  well.  Every  teacher  will  be  able  to  multiply  problems  after 
these  models  to  suit  his  own  requirements. 

The  questions,  which  accompany  the  problems,  form  another 
essential  feature  in  the  plan  of  instruction  here  presented. 
They  are  intended  not  only  to  direct  the  student's  attention  to 
the  most  important  points,  but  also  to  stimulate  thought  by  sug- 
gesting inferences  to  which  the  principles  stated  legitimately 
lead. 

These  questions,  moreover,  will  indicate  to  the  teacher  the 
manner,  in  which  it  is  intended  that  the  book  should  be  studied. 
Care  should  be  taken  not  to  overstrain  the  memory,  but  to  dis- 
tribute the  necessary  burthen  through  many  lessons.  Thus,  for 
the  first  seven  chapters,  the  student  should  not  be  expected  to 
reproduce  the  symbols  and  reactions,  nor  even  to  call  the 
names  of  the  substances  represented,  except  those  of  the  sub- 
stances with  which  he  is  familiar.  It  will  be  sufficient  for 
the  time  if  he  understands  the  principles  which  the  symbols 
illustrate,  and  the  relations  of  the  parts  of  the  reactions,  al- 
though as  yet  these  conventional  signs  may  have  for  him  no 
more  definite  meaning  than  the  paradigms  of  a  grammar.  As 
he  advances  through  chapters  VIII.  and  IX.,  he  should  be 
expected  to  familiarize  himself  with  the  names  of  the  com- 
pounds, and  should  begin  to  reproduce  the  symbols.  "When 
reciting  on  chapter  X.  he  should  be  called  upon  to  give  not 
only  the  names  of  all  the  symbols,  but  also  the  symbols  corre- 
sponding to  all  the  names,  and  so  on  for  the  rest  of  the  book. 
In  reviewing  the  book  a  full  knowledge  of  the  names  and  sym- 
bols will  be  of  course  expected  from  the  first.  The  questions 
and  problems  appended  to  each  chapter  will  give  the  student 
a  clear  idea  of  what,  in  any  case  will  be  required*  The  author 
has  been  in  the  habit  of  writing  out,  for  his  own  class,  similar 
problems  on  separate  cards,  together  with  the  names,  symbols, 
reactions  or  other  data<  which  may  in  any  case  be  given. 
These  cards  are  distributed  at  the  beginning  of  each  recitation, 
and  the  student  is  not  called  upon  to  recite  until  he  has  placed 
his  work  upon  the  blackboard.  This  plan  obviates  many  prac- 
tical difficulties,  and  has  been  found  to  work  with  great  success. 


vi  PEEFACE.       ' 

In  arranging  the  chapters  of  Part  I.  the  only  aim  has  been 
to  present  the  several  subjects  in  a  logical  sequence,  and  in 
other  respects  the  order  adapted  is  not  always  the  most  philo- 
sophical; but  the  teacher  can  of  course  vary  the  order  at 
pleasure.  So  also  in  regard  to  Part  II.,  the  teacher  may  pre- 
fer to  take  up  the  elements  in  his  lectures  in  a  different  order 
from  that  in  which  they  are  there  classified,  but  then  the  sev- 
eral sections  may  be  studied  in  any  order  he  would  be  likely  to 
adopt  with  equal  advantage. 

The  philosophy  of  chemistry  has  been  developed  in  this 
book  according  to  the  "  modern  theories  " ;  and  the  author 
would  acknowledge  his  obligations  to  the  recent  works  of 
Frankland,  Kekule,  Miller,  Naquet,  Roscoe,  Watts,  William- 
son, and  Wurtz,  all  of  which  he  has  freely  consulted.  Care- 
ful attention  has  been  given  to  the  chemical  notation  ;  and  a 
method  has  been  devised  of  writing  rational  symbols  which, 
while  it  fully  exhibits  the  relations  of  the  parts  of  the  mole- 
cule, condenses  the  formula,  and  saves  space  and  labor  in 
printing.  The  nomenclature  adopted  accords  with  what  the 
author  regards  as  the  best  English  usage.  Innovations  would 
hardly  be  justified  in  an  elementary  work,  but  every  one  must 
regret  that  the  usage  is  not  more  uniform  and  consistent  with 
the  modern  chemical  philosophy.  In  the  chapter  on  this  sub- 
ject, the  old  names  are  given  with  the  new.  Lastly,  the  me- 
tric system  of  weights  and  measures,  and  the  centigrade  saale 
of  the  thermometer,  are  used  throughout  the  book. 

In  reviewing  the  work  for  a  new  edition,  the  chapter  on  the 
Electrical  Relations  of  the  Atoms  has  been  rewritten,  and  the 
facts  presented  in  the  light  of  a  new  theory,  which  it  is  hoped 
will  bring  them  into  more  intelligible  relations.  Important 
additions  have  also  been  made  to  the  chapters  on  Stochiometry 
and  Chemical  Equivalency,  and  a  new  chapter  has  been  added 
which  treats  of  a  number  of  interesting  but  highly  complex 
compounds  that  were  not  included  in  the  general  plan  of  the 
book,  and  may  be  more  advantageously  studied  in  an  appen- 
dix. Moreover,  throughout  the  book  the  text  has  been  altered 
wherever  corrections  have  been  made  necessary  by  the  recent 
progress  of  the  science. 

CAMBRIDGE,  September  1, 1871. 


CONTENTS. 


PAET    I. 

CHAPTER 

I.  INTRODUCTION 1 

II.  FUNDAMENTAL  CHBMICAL  RELATIONS         ...         7 

III.  MOLECULES 11 

IV.  ATOMS    . 24 

V.  CHEMICAL  NOTATION 33 

VI.  STOCHIOMETRY 41 

VII.  CHEMICAL  EQUIVALENCY 54 

VIII.  CHEMICAL  TYPES 62 

IX.  BASES,  ACIDS,  AND  SALTS 80 

X.  CHEMICAL  NOMENCLATURE 100 

XI.  SOLUTION  AND  DIFFUSION 107 

XII.  THERMAL  RELATIONS  OP  THE  ATOMS  ....  114 

XIII.  MOLECULAR  WEIGHT  AND  CONSTITUTION      .        .        .126 

XIV.  CRYSTALLINE  FORMS 137 

XV.  ELECTRICAL  RELATIONS  OF  THE  ATOMS        .        .        .155 

XVI.  RELATIONS  OF  THE  ATOMS  TO  LIGHT         .        .        .174 

XVII.  CHEMICAL  CLASSIFICATION  .        .        .        .191 


viii  CONTENTS. 


PART    II. 

CHAPTER  PAGB 

XVIII.    THE  PERISSAD  ELEMENTS 201 

DIVISION    I.    Hydrogen 201 

"          II.    Fluorine.  —  Chlorine. — Bromine.  —  Iodine  207 
'*        III.     Sodium.— Potassium      .        .        .        .        .213 

"         IV.     Silver *  220 

"           V.     Thallium .        .  222 

VI.     Gold ,  222 

"       VII.    Boron 228 

"  VIII.  Nitrogen.  —  Phosphorus.  —  Arsenic.  —  Anti- 
mony.—  Bismuth 233 

"        IX.    Vanadium 291 

"          X.     Uranium 293 

"        XI.     Columbiura.  — Tantalum 296 

XIX.    THE  ARTIAD  ELEMENTS    .        .        .     .  .        .       .  300 

DIVISION    I.    Oxygen .  300 

"         II.    Sulphur.  —  Selenium.  —  Tellurium       .        .  308 
"        III.    Molybdenum.  —  Tungsten        .        .        .        .321 

"        IV.     Copper.  —  Mercury 328 

"          V.     Calcium.  —  Strontium. — Barium. — Lead       .  340 
"        VI.,  VII.  Magnesium. — Zinc. — Indium. — Cadmium  354 
"    VIII.,  IX.    Glucinum.  —  Yttrium.  —  Erbium.  —  Ceri- 
um.—  Lanthanum.  —  Didymium  .        .        .  363 

"         X.    Nickel. —  Cobalt 365 

"       XL    Manganese.  —  Iron 373 

"      XII.     Chromium 398 

"     XHI.    Aluminum 408 

"     XIV.  to  XVI.    The  Platinum  Metals.  — Ruthenium.— 

Osmium. — Rhodium. — Iridium. — Palladium  418 

"  XVII.  to  XIX.    Titanium.  —  Tin.  —  Zirconium  .        .  430 

"      XX.     Silicon 444 

"  XXI.  Carbon.  —  Carbon  and  Oxygen,  or  Sulphur. — 
Carbon  and  Nitrogen.  —  Carbon  and  Hydro- 
gen.—  Alcohols  and  their  Derivatives  .  .  458 


XX.    APPENDIX.    Complex   Amines    and    Amides,   Chlorals, 

Mellitic  Acid,  Quinones,  Electrical  Measurements       .    534 
TABLE  I.    French  Measures, 
"     II.    Elementary  Atoms. 
"  III.     Specific  Gravity  of  Gases  and  Vapors. 

LOGARITHMS  AND   ANTILOGARITHMS 


FIRST  PRINCIPLES 


OP 


CHEMICAL   PHILOSOPHY. 


PAKT    I. 

CHAPTER    I. 

INTRODUCTION. 

1.  Definitions.  —  The  volume  of  a  body  is  the  space  it  fills, 
expressed  in  terms  of  an  assumed  unit  of  volume.     The  weight 
of  a  body,  as  the  word  is  used  in  chemistry  and  generally  m 
common  life,  is  the  amount  of  material  which  the  body  con- 
tains compared  with  that  in  some  other  body  assumed  as  the 
unit  of  weight.     The  specific  gravity/  of  a  body  is  the  ratio  of 
its  weight  to  that  of  an  equal  volume  of  some  substance  which 
has  been  selected  as  the  standard.     Solids  and  liquids  are  al- 
ways compared  with  water  at  its  greatest  density,  which  is  at 
4°  centigrade,  and  hence  the  numbers  which  stand  for  their 
specific  gravities  express  how  many  times  heavier  they  are 
than  an  equal  volume  of  water  at  this  temperature.     Gases, 
however,  are  most  conveniently  compared  with  the  lightest  of 
all  known  forms  of  matter,  namely,  hydrogen,  and  in  this  book 
the  number  which  indicates  the  specific  gravity  of  a  gas  ex- 
presses how  many  times  heavier  it  is  than  an  equal  volume  of 
hydrogen,  compared  under  the  same  conditions  of  temperature 
and  pressure. 

2.  Volume  and  Weight.  —  All   experimental  science   rests 
upon  accurate  measurements  of  these  fundamental  elements, 
and  it  is  therefore  very  important  that  there  should  be  a  gen- 
eral agreement  among  scientific  men  in  regard  to  them.     This 

1 


has  been  secured  by  the  almost  universal  adoption  of  the 
French  system  of  measures  and  weights  in  all  scientific  inves- 
tigations. The  details  of  this  system  are  given  in  Table  I., 
and  they  require  no  further  explanation.  Its  great  advan- 
tage over  our  ordinary  English  system  is  not  only  in  its  deci- 
mal subdivision,  but  also  in  the  simple  relation  which  exists 
between  the  units  of  measure  and  of  weight.  Since  the  unit 
of  weight  is  the  weight  of  the  unit  volume  of  water,  and  since 
the  specific  gravity  of  solids  and  liquids  is  always  referred  to 
water,  as  the  standard,  it  is  always  true  in  this  system  that 

W=  VX  Sp.  Gr.  [1] 

If  the  volume  is  given  in  cubic  centimetres,  the  weight  ob- 
tained is  in  grammes ;  but  if  the  volume  is  given  in  cubic  deci- 
metres or  litres,  the  weight  is  found  in  kilogrammes.  In  this 
formula,  Sp.  Gr.  stands  for  the  specific  gravity  referred  to 
water.  If  the  specific  gravity  is  referred  to  hydrogen,  as  in 
the  case  of  gases,  the  value  must  be  reduced  to  the  water- 
standard  before  using  it  in  the  formula.  The  reduction  is 
easily  made,  by  multiplying  by  0.0000896,  a  fraction  which 
is  simply  the  specific  gravity  of  hydrogen  itself  referred  to 
water.  Using  Sp.  Gr.  to  represent  the  specific  gravity  of  a 
gas  referred  to  hydrogen,  the  formula  becomes 

W=  V  X  Sp.  Gr.  X  0.0000896,  [2] 

and  may  then  be  used  in  all  calculations  connected  with  the 
weight  and  volume  of  aeriform  bodies.  In  such  calculations,  in 
order  to  avoid  the  long  decimal  fractions  which  the  use  of  the 
gramme  entails,  Hofmann  has  proposed  to  introduce  into 
chemistry  a  new  unit  of  weight  which  he  calls  the  crith.  This 
unit  is  the  weight  of  one  cubic  decimetre  or  litre  of  hydrogen 
gas  at  the  standard  temperature  and  pressure,  and  is  equal  to 
0.0896  grammes.  If  now  we  estimate  the  weight  of  all  gases 
in  criths,  and  let  W  represent  this  weight,  while  W  represents 
the  weight  in  grammes,  and  V  the  volume  in  litres,  we  shall 
also  have 

W  =  V  X  Sp.  Gr.  and  W  =  W  X  0.0896,     [3] 

and  all  problems  of  this  kind  will  then  be  reduced  to  their 
simplest  terms. 


INTRODUCTION.  3 

The  specific  gravity  of  gases  is  also  frequently  referred  to 
dry  air,  which  for  many  reasons  is  a  convenient  standard. 
The  weight  of  one  litre  of  air  under  standard  conditions  is 
1.293187  grammes.  Hence,  representing  specific  gravity  re- 
ferred to  air  by  Sp.  (B>r.  we  have 

Sp.  Gr.  :  Sp.  (Sr.  =  1.2932  :  0.0896, 
or 

Sp.  Gr.  =  Sp.<£>r.  X  14.42,    • 
and 

Sp.  <&r.  —  Sp.  Gr.  X  0.06929. 

3.  Chemistry  and  Physics.  —  Among  material  phenomena 
we  may  distinguish  two  classes.  First,  those  which  are  mani- 
fested without  a  loss  of  identity  in  the  substances  involved. 
Secondly,  those  which  are  attended  by  a  change  of  one  or 
more  of  the  materials  employed  into  new  substances.  The 
science  of  chemistry  deals  with  the  last  class  of  phenomena, 
that  of  physics  with  the  first,  and  hence  the  terms  chemical 
and  physical  phenomena.  An  illustration  will  make  this  dis- 
tinction plain.  When  a  bar  of  iron  is  drawn  out  into  wire,  is 
rolled  out  into  thin  leaves,  is  reduced  by  mechanical  means  to 
powder,  is  forged  into  various  shapes,  is  melted  and  cast  into 
moulds,  is  magnetized,  or  is  made  the  medium  of  an  electric 
current,  since  the  metal  does  not  in  any  case  lose  its  identity, 
the  phenomena  are  all  physical.  When,  on  the  other  hand, 
the  iron  bar  rusts  in  the  air,  is  burnt  at  the  blacksmith's  forge, 
or  is  dissolved  in  dilute  sulphuric  acid,  the  iron  is  converted 
into  a  new  substance,  iron  rust,  iron  cinders,  or  green  vitriol, 
and  the  phenomena  are  chemical.  The  distinction  between 
these  two  departments  of  human  knowledge  is  not,  however, 
so  strongly  marked  as  the  definition  would  seem  to  imply. 
In  fact  they  coalesce  at  many  points,  and  a  knowledge  of  the 
elements  of  physics  is  an  essential  preliminary  to  the  successful 
study  of  chemistry.  In  the  following  pages  it  will  be  assumed 
that  the  student  is  acquainted  with  the  most  elementary  princi- 
ples of  this  science,  and  references  will  be  made  to  the  sections 
of  the  author's  work  on  Chemical  Physics.  The  same  rela- 
tion which  physics  bears  to  chemistry  on  the  one  side,  chemis- 
try bears  to  physiology  and  the  natural-history  sciences  on  the 
other. 


4  INTRODUCTION. 

Questions  and  Problems. 

1.  Reduce  by  Table  I.  at  the  end  of  the  book, 

30  Inches  to  fractions  of  a  metre.  Ans.  0.7619  metre. 

76  Centimetres  to  inches.  Ans.  29.92  inches. 

36  Kilometres  to  miles.  Ans.  22.38  miles. 

10  Metres  to  feet  and  inches.  Ans.  32  ft.  9.7  inches. 

1  Cubic  metre  to  quarts.  Ans.  880.66  quarts. 

1  Cubic  foot  to  litres.  Ans.  28.31  litres. 

1  Pint  to  cubic  centimetres.  Ans.  567.8  cTmT,3 

1  Litre  to  cubic  inches.  Ans.  61,027  cubic  inches. 

1  Pound  Avoirdupois  to  grammes.  Ans.  453.6  grammes. 

1  Kilogramme  to  ounces  avoirdupois.  Ans.  35.27  ounces. 

1  Ounce  to  grammes.  Ans.  28.35  grammes. 

2.  If  the  globe  were  a  perfect  sphere  what  would  be  the  circum- 
ference and  what  the  diameter  in  kilometres  ? 

Ans.  Circumference  40,000  kilometres) 
Diameter  12,732.4      " 

3.  The  length  of  the  metre  was  determined  by  measuring  the  dis- 
tance between  Dunkirk  (in  France),  Latitude  51°  2'  9"  and  For- 
mentera  (one  of  the  Balearic  Islands),  Latitude  38°  39'  56",  both 
on  the  same  meridian.     This  distance  was  found  by  triangulation  to 
be  equal  to  730,430  toises.     What  is  the  length  of  a  metre  in  terms 
of  this  old  French  unit  of  measure  ?     What,  also,  was  the  length 
measured  in  English  miles  ?     No  account  is  to  be  taken  of  the  ellip- 
ticity  of  the  earth.  Ans.  The  metre,  0.5314  toise. 

The  length  was  854  miles. 

4.  The  Sp.  Gr.  of  iron  is  7.84.     What  is  the  weight  of  10  c.~m.3 
of  the  metal  in  grammes  ?     What  is  also  the  weight  in  kilogrammes 
of  a  sphere  of  iron  whose  diameter  equals  one  decimetre  ? 

Ans.  78.4  grammes  and  4.105  kilogrammes. 

5.  What  is  the  weight  in  grammes  of  50  c.  in.3  of  oil  of  vitriol, 
when  the  Sp.  Gr.  of  the  liquid  is  1.8?  Ans.  90  grammes. 

6.  The  Sp.  Gr.  of  alcohol  being  0.8,  what  volume  in  litres  would 
weigh  7.2  kilogrammes?  Ans.  9  litres. 

7.  Assuming  that  the  earth  is  spherical,  and  its  mean  Sp.  Gr.  5.67, 
what  would  be  its  weight,  using  as  the  unit  of  weight  a  kilometre 
cube  of  water  at  its  greatest  density  ?         Ans.  6,130,000,000,000. 

8.  Determine  the  Sp.  Gr.  of  absolute  alcohol  from  the  following 
data:  —  weight  of  empty  bottle  4.326;  weight  of  same  filled  with 
water  19.654  ;  weight  of  same  filled  with  alcohol  16.741. 

Ans.  0.8095. 


INTRODUCTION.  5 

9.  Determine  the  Sp.  Gr.  of  lead  from  the  following  data :  — 
weight  of  bottle  filled  with  water    19.654;   weight  of  lead  shot 
15.456 ;  weight  of  bottle  filled  in  part  with  the  shot  and  the  rest 
with  water  33.766.  Ans.  11.5. 

10.  Determine  the  Sp.  Gr.  of  iron  from :  —  weight  of  iron  in  air 
3.92  ,  weight  under  water  3.42.  Ans.  7.84. 

11.  Determine  Sp.  Gr.   of  wood  from :— weight  of  wood  in  air 
25.35  ;  weight  of  sinker  under  water  9.77 ;  weight  of  wood  with 
sinker  under  water  5.10  grammes.  Ans.  0.8445. 

12.  How  much  volume  must  a  hollow  sphere  of  copper  have, 
weighing  one  kilogramme,  which  will  just  float  in  water  ?     What 
must  be  the  volume  of  the  copper  ?     Sp.  Gr.  of  copper  8.8. 

Ans.  One  cubic  dicemetre  and  113.6  c.  m.3 

13.  How  much  volume  must  a  hollow  cylinder  of  iron  have,  which 
weighs  10  kilogrammes  and  sinks  one  half  in  water,  and  what  must       * 
be  the  volume  of  the  metal  ?   Ans.  20  and  1.276  cubic  decimetres. 

14.  What  is  the  weight  in  grammes  (under  standard  conditions) 
of  128  c.~m.3  of  oxygen  gas  (Sp.  Gr.  =  16)  ? 

Ans.  0.1834  grammes. 

15.  How  many  litres  of  carbonic  anhydride  gas  (Sp.  Gr.  =  22) 
would  weigh  (under  normal  conditions)  4.480  kilogrammes? 

Ans.  2274  litres. 

16.  Solve  the  last  two  problems  by  [3],  and  show  in  what  respect 
the  method  differs  from  that  indicated  by  [2]. 

1 7.  What  is  the  weight  in  criths  (under  standard  conditions)  of 
one  litre  of  nitrogen  gas  (Sp.  Gr.  =  14),  of  one  litre  of  chlorine  gas 
(Sp.  Gr.  =  35.5),  of  one  litre  of  marsh  gas  (Sp.  Gr.  =  8),  and  of 
one  litre  of  ammonia  gas  (Sp.  Gr.  =  8.5)  ? 

Ans.  14,  35.5,  8,  and  8.5  criths  respectively. 

18.  What  is  the  weight  in  grammes  of  one  litre  of  each  of  the 
same  gases  under  the  same  conditions  ? 

Ans.  1.254,  3.180,  0.7165,  and  0.7617  respectively. 

19.  The  weight  of  one  litre  of  hydrochloric   acid  gas  is  1.642 
grammes  ;  of  carbonic  oxide  gas  1.2500  grammes;  of  cyanogen  gas         / 
2.335  grammes,  and  of  hydrogen  gas  0.0896  grammes.     What  is  the 
specific  gravity  of  each  of  these  gases  referred  to  air  ? 

Ans.  1.270,  0.9665,  1.806,  and  0.0693  respectively. 

20.  What  is  the  volume   (under  standard  conditions)   of  12.54 
grammes  of  nitrogen  gas,  when  specific  gravity  referred  to  air  is 
0.9703?  Ans.  10  litres. 


6  INTRODUCTION. 

21.  What  is  the  weight  of  one  litre  of  air  in  criths? 

Ans.  14.42. 

22.  What  would  be  the  ascensional  force  of  one  thousand  litres 
of  hydrogen,  under  normal  conditions  ? 

Ans.  The  ascensional  force  is  the  difference  between  the  weight 
of  the  hydrogen  and  that  of  the  air  displaced.  Hence  in 
the  present  example,  the  ascensional  force  would  be  14,420 
—  1000  =  13420  criths,  or  1,201  grammes. 

23.  What  is  the  value  of  a  crith  in  grains,  English  weight. 

Ans.  1.382  grains. 


CHAPTER   II. 

FUNDAMENTAL    CHEMICAL    RELATIONS. 

4.  Compounds  and  Elements. — With  sixty^three  exceptions, 
all  known  substances,  by  various  chemical  processes,  may 
be  decomposed,  and  hence  are  called  chemical  compounds; 
while  the  sixty-three  substances  which  have  as  yet  never 
been  resolved  into  simpler  parts  are  called  chemical  elements. 
There  is  some  reason  for  believing  that  many,  if  not  all,  of 
these  elementary  substances  may  hereafter  be  decomposed,  and 
hence  they  can  only  be  considered  chemical  elements  provis- 
ionally ;  but,  however  this  may  be,  all  known  materials  may  still 
be  regarded  as  formed  by  the  union  of  the  particles  of  one  or 
more  of  these  sixty-three  substances.  A  list  of  the  chemical 
elements  is  given  in  Table  II.  The  names  of  the  more  abun- 
dant, or  otherwise  more  important  elements  are  printed  in  Ro- 
man letters.  The  others  are  very  rare  substances^  and  are 
practically  unimportant.  Of  these  elementary  substances  more 
than  three  fourths  possess  metallic  properties,  and  among  them 
are  all  the  useful  metals,  including  the  liquid  metal  mercury. 
The  rest  present  every  variety  of  physical  character.  Oxygen, 
hydrogen,  and  nitrogen  are  permanent  gases.  Chlorine,  and 
probably  fluorine,  though  gases  under  ordinary  conditions,  may 
by  pressure  and  cold  be  condensed  to  liquids.  Bromine  is  a 
very  volatile  liquid ;  and  among  the  solids  we  have  every  gra- 
dation between  the  highly  volatile  iodine,  or  the  easily  fusible 
phosphorus,  on  the  one  hand,  and  carbon,  which  has  never 
even  been  melted,  on  the  other.  We  find,  also,  among  the  ele- 
ments every  difference  as  regards  density.  Hydrogen  gas  is 
the  lightest,  and  the  metal  platinum  the  heaviest  substance 
known.  Several  of  the  elementary  substances  occur  in  a  free 
state  in  nature,  for  example,  oxygen  and  nitrogen  in  the  at- 
mosphere, carbon  in  the  coal  beds,  sulphur  in  the  neighborhood 
of  active  volcanoes,  iron  in  meteoric  stones,  while  arsenic,  an- 


8  FUNDAMENTAL  CHEMICAL  RELATIONS. 

timony,  bismuth,  copper,  gold,  silver,  mercury,  and  platinum, 
with  a  few  other  rare  associates,  are  sometimes  found  In  a 
more  or  less  pure  state  in  metallic  veins.  Gold  and  platinum 
are  usually  found  in  a  free  condition,  though  as  a  rule  slightly 
alloyed  with  their  associated  metals  ;  but  all  the  other  elements 
are  generally  found  in  combination,  and  the  greater  number 
appear  in  nature  only  in  this  condition.  From  such  compounds 
the  elements  may  be  extracted  by  various  chemical  processes, 
which  will  appear  as  we  proceed.  Among  these  elements  the 
useful  metals  are  the  tools  of  civilization,  carbon  is  our  uni- 
versal fuel,  while  sulphur,  phosphorus,  arsenic,  chlorine,  bro- 
mine, and  iodine  have  found  important  applications  in  the  arts, 
and  are  therefore  articles  of  commerce  ;  but  the  greater  number 
of  the  elements  are  only  to  be  seen  in  the  chemist's  laboratory, 
and  are  solely  objects  of  chemical  investigation.  The  elements 
are  distributed  in  nature  in  very  unequal  proportions.  At 
least  one  half  of  the  solid  crust  of  the  globe,  eight  ninths  of 
the  water  on  its  surface,  and  one  fifth  of  the  atmosphere  which 
surrounds  it,  consist  of  the  one  element,  oxygen.  Moreover, 
the  other  elements  are  usually  found  in  combination  with 
oxygen,  so  that  oxygen  may  be  regarded  as  the  cement  by 
which  these  elementary  parts  of  the  world  are  held  together. 
Next  in  abundance  is  silicon,  which,  after  oxygen,  is  the  chief 
constituent  of  the  rocks,  and  makes  up  about  one  fourth  of  the 
earth's  crust.  Silicon  is  always  found  combined  with  oxygen, 
and  more  than  one  half  of  the  oxygen  of  the  globe  is  in  com- 
bination with  this  element.  Hence,  the  compound  of  the  two, 
which  we  call  silica  or  quartz,  must  make  up  more  than  one 
half  of  our  solid  globe,  at  least  as  far  as  its  composition  is 
known.  After  silicon  in  the  order  of  abundance  would  follow 
the  elements  aluminum,  calcium,  magnesium,  potassium,  so- 
dium, iron,  carbon,  sulphur,  hydrogen,  chlorine,  nitrogen, 
which,  without  attempting  to  discriminate  between  them,  make 
up  altogether  very  nearly  the  other  fourth  of  the  earth's  mass ; 
for  the  remaining  fifty  elements  —  including  all  the  useful 
metals  except  iron  —  do  not  constitute  altogether  more  than 
one  one-hundredth.  Of  the  sixty-three  known  elements,  then, 
thirteen  alone  make  up  at  least  -^j  of  the  whole  known  mass 
of  the  earth. 

5.  Analysis  and  Synthesis.  —  The  composition  of  a  chemical 


FUNDAMENTAL  CHEMICAL  RELATIONS.  9 

compound  may  be  made  evident  in  two  ways.  First,  by  break- 
ing up  the  compound  into  its  constituent  parts ;  secondly,  by 
reuniting  these  parts  and  reproducing  the  original  substance. 
The  first  of  these  methods  of  proof  is  called  analysis,  the  sec- 
ond, synthesis.  The  study  of  the  processes  by  ^vhich  the  com- 
position of  a  body  may  be  discovered,  and  the  relative  amounts 
of  its  various  constituents  determined,  forms  an  important 
branch  of  practical  chemistry,  which  is  known  as  Chemical 
Analysis,  and  this  is  subdivided  into  Qualitative  and  Quantita- 
tive Analysis,  according  to  the  object  we  have  in  view.  Syn- 
thesis is  chiefly  used  to  prove  the  results  of  analysis. 

6.  Law  of  Definite  Proportions.  —  Numberless  analyses 
have  proved  that  any  given  chemical  compound  always  contains 
the  same  elements  combined  in  the  same  proportions.  Thus, 
when  we  analyze  water,  sugar,  and  salt,  we  always  obtain  the 
result  given  below ;  and  this  result  is  invariable,  saving  small 
errors  of  observation,  from  whatever  source  these  materials 
may  be  drawn.  The  composition  is  given  in  per  cents,  as  is 
usual  in  such  cases. 

Water  (Dumas).  Salt.  Sugar  (Peligot). 

Hydrogen,  11.112  Sodium,    39.32  Carbon,       42.06 

Oxygen,      88.888  Chlorine,  60.68  Hydrogen,    6.50 

Oxygen,     51.44 
100.  100.  100. 

Chemists  have  not  yet  succeeded  in  making  sugar  by  com- 
bining its  elements,  but  the  synthesis  both  of  water  and  salt  is 
easily  effected,  and  illustrates  still  more  forcibly  the  same  law. 
Thus  we  may  mix  together  hydrogen  and  oxygen  gas  in  any 
proportion,  but  when,  by  passing  an  electric  spark  through  the 
mixture,  we  cause  the  elements  to  combine,  then  the  gases 
unite  in  the  exact  proportion  indicated  above,  and  any  excess 
of  one  or  the  other  which  may  be  present  is  left  over.  The 
law  of  definite  proportions  gives  to  chemistry  a  mathematical 
basis ;  for,  since  the  analyses  of  all  compounds  have  been  made 
and  tabulated  in  a  way  that  will  be  soon  explained,  it  is  always 
possible,  when  the  weight  of  a  compound  is  given,  to  calculate 
the  weights  of  its  constituents,  and,  when  the  weight  of  one  of 
its  elements  is  known,  to  calculate  the  weights  of  all  the  other 
elements  present. 


10  FUNDAMENTAL  CHEMICAL  RELATIONS. 

7.  Mixture  and  Chemical  Compound.  —  The  law  of  definite 
proportions  gives  a  simple  criterion  for  distinguishing  between 
a  mixture  and  a  true  chemical  compound.    In  the  first  the  ele- 
ments may  be  mixed  in  any  proportion,  but  in  the  true  com- 
pound they  are  always  combined /in  definite  proportions.    Thus 
we  may  mix  together  copper-filings  and  sulphur  in  any  propor- 
tion, but  as  soon  as  we  apply  heat,  and  cause  the  elements  to 
combine,  then  the  copper  combines  with  one  half  of  its  own 
weight  of  sulphur,  and  the  excess  of  either  element  above 
these  proportions  is  discarded.     Again,  in  a  mixture  however 
homogeneous,  we  can   generally,  by  mechanical  means  alone, 
distinguish  the  ingredients.    Thus,  in  the  mixture  just  referred 
to,  a  microscope  would  show  the  grains  of  sulphur  and  metallic 
copper,  with  all  their  characteristic  appearances ;  and  by  means 
of  carbonic  sulphide  we  can  easily  dissolve  out  all  the  sulphur 
from  the  mixture ;  but  after  the  chemical  union   has  taken 
place,  the  characteristic  properties  of  the  elements  are  merged 
in  those  of  the  compound,  and  no  such  simple  mechanical  sep- 
aration is  possible.     But  although  these  distinctions  are  gener- 
ally sufficient,  nevertheless  we  find  in  some  alloys,  in  solutions, 
and  in  a  few  other  classes  of  compounds,  less  intimate  condi- 
tions of  chemical  union  where  these  criterions  fail. 

8.  Law  of  Multiple  Proportions.  —  It  is  generally  the  case 
that  the  same  elements  unite  in  more  than  one  proportion,  form- 
ing two  or  more  different  compounds.     Now  we  always  find 
that  the  proportions  of  the  elements  in  such  compounds  are 
simple  multiples  of  each  other.     This  law  is  best  illustrated 
by  the  compounds  of  nitrogen  and  oxygen,  which  are  five  in 
number,  and  have  the  names  indicated  in  the  table  below.     In 
order  to  make  evident  the  law,  we  give,  not  the  percentage 
composition  as  above,  but  the  amount  of  oxygen,  which  is  in 
each  case  combined  with  one  and  three  fourths  parts  of  nitro- 
gen. 

COMPOUNDS  OF  NITROGEN  WITH  OXYGEN. 

Nitrogen.  Oxygen.  Nitrogen.  Oxygen. 

By  -weight.        By  weight.        By  volume.      By  volume. 

Nitrous  Oxide,  1.75  1  2  1 

Nitric  Oxide,  1.75  2  2  2 

Nitrous  Anhydride,  1.75  3  2  3 

Nitric  Peroxide,  1.75  4  2  4 

Nitric  Anhydride,  1.75  5  2  5 


CHAPTER   III. 

MOLECULES. 

9.  Molecules.  —  In  order  to  bring  the  facts  of  chemistry  into 
relation  with  each  other,  and  unite  them  in  an  harmonious  sys- 
tem, the  following  theory,  first  proposed  by  the  English  chemist, 
Dalton,  and  known  as  the  Atomic  Theory,  is  generally  accepted 
by  chemists.     This  theory  assumes,  in  the  first  place,  that  every 
body,  whatever  its  substance  may  be,  is  formed  by  the  aggre- 
gation of  minute  particles  of  the  same  kind,  which  cannot  be 
further  subdivided  without  destroying  the  identity  of  the  sub- 
stance.    Thus  a  lump  of  sugar  is  an   aggregate  of  minute 
particles  of  sugar.     If  the  sugar  is  burnt,  these  particles  will 
be  further  subdivided ;  but  the  sugar  will  be  thus  changed  into 
new  substances.     In  like  manner,  a  drop  of  water  is  an  aggre- 
gate of  minute  particles  of  water.     By  passing  a  current  of 
electricity  through  the  drop,  these  particles  will  be  subdivided, 
but  then  we  shall  have  no  longer  water,  but  the  two  elemen- 
tary gases,  oxygen  and  hydrogen.     The  smallest  particles  of 
any  substance  which  can  exist  by  themselves,  we  call  molecules. 

10.  Physical  Properties  of  Matter.  —  The  physical  qualities 
of  a  body  depend  solely  on  the  relations  of  its  molecules.     The 
physicist  has  therefore  no  occasion  to  continue  the  subdivision 
beyond  the  molecule,  which  is  his  unit. 

Solid.  —  In  a  solid  the  molecules  firmly  cohere,  and  the 
force  which  binds  them  together  has  been  called  cohesion.  On 
the  form  and  size  of  the  molecules,  and  also  on  the  mode  of 
aggregation,  is  supposed  to  depend  the  crystalline  form  of  each 
substance,  which  is  one  of  the  most  important  and  character- 
istic properties  of  matter,  and  one  to  which  we  shall  have 
occasion  hereafter  to  refer.  On  certain  relations  of  the  mole- 
cules, which  we  do  not  fully  understand,  depend  undoubtedly 
elasticity,  tenacity,  ductility  or  malleability,  hardness,  transpar- 
ency, diathermancy,  and  the  allied  qualities  of  solid  bodies. 


12  MOLECULES. 

Liquid.  —  In  the  liquid  condition  of  matter  the  molecules 
have  more  freedom  of  motion  than  in  the  solid,  but  still  the 
motion  is  circumscribed  within  the  liquid  mass.  Moreover,  a 
certain  cohesion  still  exists  between  the  molecules,  and  on  this 
depends  the  form  of  the  rain-drop.  The  various  phenomena 
of  capillary  action  also  are  effects  of  the  cohesion  of  the  liquid 
molecules  modified  by  their  adhesion  to  the  surfaces  of  solids, 
and  the  solvent  power  of  liquids  is  a  still  further  effect  of  the 
same  mutual  action.  Connected  also  with  this  freedom  of 
molecular  motion  is  the  property  of  liquids  of  transmitting 
pressure  in  all  directions,  and  the  well-known  principles  of 
hydrostatics  to  which  it  leads;  but  this  property  belongs  to 
the  third  condition  of  matter  as  well. 

Gas.  —  In  the  aeriform  condition  of  matter,  the  motion  of 
ihe  molecules  is  only  circumscribed  by  the  walls  of  the  con- 
taining vessel,  or  by  some  force  acting  on  the  mass  from  with- 
out. The  molecules  of  a  gas  are  constantly  beating  against 
the  walls  which  confine  them,  and  were  they  not  thus  restrained 
would  fly  off  into  space.  The  molecules  of  the  atmosphere 
are  restrained  by  the  force  of  gravitation,  and,  as  they  fly  up- 
wards like  a  ball  thrown  into  the  air,  they  are  at  last  brought 
to  rest,  and  fall  back  again  to  the  earth.  Hence  gases  always 
exert  pressure  against  any  surface  with  which  they  are  in  con- 
tact, and  we  measure  the  pressure,  or,  as  we  frequently  call  it, 
the  tension  of  the  gas,  by  the  height  to  which  it  will  raise  a 
column  of  mercury.  Chem.  Phys.  (158).  The  instrument 
used  for  this  purpose  is  called  a  barometer. 

The  height  of  the  mercury  column  which  represents  the 
pressure  or  tension  of  a  gas  is  always  represented  by  H. 

In  our  latitude,  at  the  surface  of  the  sea,  the  atmosphere  in 
its  normal  conditions  will  raise  a  column  of  mercury  76  c.  m. 
high.  Hence  If  =  76,  and  to  this  standard  we  always  refer  in 
comparing  together  the  volumes  of  different  gases. 

11.  Mariotte's  Law.  —  The  most  characteristic  feature  of 
the  aeriform  condition  is  the  great  change  of  volume  which 
gases  undergo,  under  varying  pressure,  and  the  special  law 
of  compressibility  which  they  obey.  If  we  represent  by  If 
and  H'  two  conditions  of  pressure  to  which  the  same  body  of 
gas  is  at  different  times  exposed,  then  the  law  is  expressed  by 
the  formula 

V:  V'  —  H':H.  [4] 


MOLECULES.  13 

Moreover,  since  the  specific  gravity  of  a  given  mass  of  gas 
must  be  the  greater  the  less  its  volume,  it  is  also  true  that 

Sp.  Gr.  :  Sp.  Gr1.  =  H:  H>,  [5] 

and  lastly,  since  the  weight  of  a  given  volume  of  gas  is  obvi- 
ously proportional  to  its  specific  gravity,  we  also  have 

W :  W  =  H:  H1,  [6] 

in  which  W  and  W  represent  the  weight  of  an  equal  volume 
of  the  same  gas  under  the  two  pressures  H  and  H'. 

12.  Heat  a  Manifestation  of  Molecular  Motion.  —  The 
effects  of  what  we  call  heat  are  supposed  to  be  merely  mani- 
festations of  the  motion  of  the  molecules  of  bodies.  The 
greater  the  moving  power  of  the  molecule,  the  more  forcibly  it 
strikes  against  our  nerves  of  feeling,  and  hence  the  more  in- 
tense is  the  sensation  of  heat  produced ;  and  to  the  condition 
of  matter  which  produces  this  sensation  we  give  the  name  of 
temperature.  The  greater  the  moving  power  of  the  molecules, 
the  higher  the  temperature ;  the  less  the  moving  power,  the 
lower  the  temperature.  Moreover,  since  by  the  very  defini- 
tion all  molecules  at  the  same  temperature  are  in  the  condition 
to  produce  the  same  sensation  of  heat,  we  must  assume  further, 
that,  whatever  their  size  or  weight,  they  must  all  have,  at  the 
same  temperature,  the  same  moving  power.  The  light  mole- 
cule of  hydrogen  must  move  much  faster  than  the  heavy  mole- 
cule of  carbonic  anhydride  in  order  to  produce  the  same  effect. 
If  now  we  represent  the  mass  of  any  molecule  by  m,  and  by  V 
its  velocity  at  any  given  temperature,  then  the  moving  power 
will  be  represented  by  §m  F2,  Chem.  Phys.  (42),  and  this  will 
have  the  same  value  for  every  molecule  at  the  same  tempera- 
ture. With  a  few  exceptions,  all  bodies  expand  with  an  in- 
creasing temperature,  and  in  the  case  of  mercury  the  change 
of  volume  is  so  nearly  proportional  to  the  change  of  tempera- 
ture that  we  may  use  the  varying  volume  of  a  confined  mass 
of  this  liquid  as  a  measure  of  temperature.  This  is  the  sim- 
ple theory  of  the  common  mercurial  thermometer,  and  in  this 
book  we  shall  refer  all  temperatures  to  the  degrees  of  the  cen- 
tigrade scale.  These  degrees  are  purely  arbitrary ;  but  to 
each  one  corresponds  a  definite  value  of  ^m  F2,  although  we 
have  not  as  yet  been  able  to  connect  our  arbitrary  with  our 
theoretical  measure. 


14:  MOLECULES. 

When  we  increase  the  temperature  of  a  body,  we  must  of 
course  increase  the  moving  power  of  all  the  molecules,  each  by 
the  same  amount,  and  the  sum  of  the  moving  powers  which 
they  thus  acquire  is  the  legitimate  measure  of  the  amount  of 
heat  which  the  body  receives.  Hence,  while  \m  V2  represents 
the  temperature  of  a  body,  2  ±m  V2  represents  the  whole 
amount  of  heat  which  it  contains.  Practically,  however,  we 
measure  quantity  of  heat  by  an  arbitrary  standard,  and  we 
shall  use  in  this  book  as  our  unit  the  amount  of  heat  required 
to  raise  the  temperature  of  a  kilogramme  of  pure  water  from 
0°  to  1°  centigrade.  This  we  call  the  Unit  of  Neat,  and  it 
has  been  found,  by  careful  experiments,  that  this  unit  of  heat 
represents  an  amount  of  moving  power  which  is  adequate  to 
raise  a  weight  of  423  kilogrammes  one  metre,  or  to  do  any 
other  equivalent  amount  of  work. 

13.  .Expansion  by  Heat.  —  The  amount  of  expansion  which 
bodies  undergo  when  heated  has  been  carefully  measured  for 
many  different  substances,  and  the  results  are  tabulated  in  all 
works  on  physics.  Chem.  Phys.  Table  XV.  In  each  case  is 
given  the  coefficient  of  expansion,  which  is  the  small  fraction 
of  its  volume  which  a  body  increases  when  heated  one  centi- 
grade degree.  If,  now,  K  represents  this  fraction,  V  the  initial 
volume,  V  the  new  volume,  t  the  initial  temperature,  and  f 
the  new  temperature,  then,  if  we  assume  that  the  expansion  is 
proportional  to  the  temperature,  we  easily  deduce  the  formula, 
Chem.  Phys.  (239), 

V'  =  V(l  +  K(t'  —  t)).  [7] 

This  formula  serves  to  calculate  the  change  of  volume  both 
of  solids  and  gases,  which  expand,  nearly  at  least,  proportion- 
ally to  the  temperature.  The  same,  however,  is  not  true  of 
liquids,  whose  rate  of  expansion  frequently  increases,  with  the 
temperature,  very  rapidly  ;  and  for  such  bodies  we  are  obliged 
to  use  the  following  formula,  which  is  of  the  general  form  in 
which  every  algebraic  function  may  be  developed,  and  is  much 
less  simple :  — 

V  —  F(l  +  At  +  Bt*  +  Ct*  +  $c.).      [8] 

In  this  formula,  V  represents  the  required  volume  at  some 
temperature,  t,  and  F",  the  volume  at  0°,  which  is  assumed  to 
V  k^owu  ;  while  A,  B,  G,  &c.,  are  numerical  constants,  which 


MOLECULES.  15 

have  been  determined  by  experiment  in  the  case  of  most  liquids. 
Chem.  Phys.  (255). 

Both  solids  and  liquids  expand  with  irresistible  force,  and 
we  have,  therefore,  only  this  one  effect  to  consider  in  regard  to 
the  action  of  heat  upon  them.  It  is  different,  however,  with 
gases.  By  enclosing  a  gas  in  a  tight  vessel,  we  can  raise  its 
temperature  without  changing  its  volume,  except  so  far  as  the 
vessel  itself  becomes  enlarged  by  the  heat.  The  effect  of  the 
heat  is,  then,  to  increase  the  tension  or  pressure  of.  the  gas. 
Hence,  in  the  case  of  a  gas,  we  may  have  two  distinct  effects ; 
first,  an  increase  of  volume,  when  the  pressure  is  constant ; 
secondly,  an  increase  of  tension,  when  the  volume  is  constant. 
The  increased  volume  may  always  be  calculated  from  the  in- 
itial volume  and  difference  of  temperature,  by  means  of  the 
formula, 

V  =  F(l  +  0.00366  (tf  —  0),  [9] 

which  differs  from  that  just  given  only  in  that  the  numerical 
value  has  been  substituted  for  K,  —  this  being  the  same  for  all 
gases.  On  the  other  hand,  the  increased  tension  may  always 
be  calculated  from  the  initial  tension,  by  means  of  the  corre- 
sponding formula, 

H1  =  H(l  +  0.00366  (tf  —  0),  [10] 

in  which  ffaud  H1  stand  for  the  heights  of  the  mercury  col- 
umns which  measure  the  initial  and  final  tension  respectively. 
The  last  formula  is  easily  deduced  from  the  first,  on  the  prin- 
ciples of  Mariotte's  law,  stated  above.  Chem.  Phys.  (261) 
and  [201]. 

Variations  of  temperature  produce  such  important  changes 
in  the  volume  and  specific  gravity  of  all  bodies,  and  especially 
of  gases,  that  it  becomes  frequently  essential,  before  compar- 
ing together  different  observations,  to  reduce  them  all  to  some 
standard  temperature.  Most  scientific  men  use,  as  this  stand- 
ard temperature,  0°  centigrade,  and  scientific  measures  are 
generally  adjusted  to  this  standard  ;  but  60°  Fahrenheit,  corre- 
sponding to  15°.5  centigrade,  is  often  a  more  convenient  stand- 
ard, because  it  is  nearer  the  mean  temperature  of  the  air,  and 
is,  therefore,  not  unfrequently  employed. 

14.    Change  of  State.  —  Many  substances  are  capable  of  ex- 


16  MOLECULES. 

isting  in  all  the  three  conditions  of  matter.  Now,  we  find  that 
whenever  a  solid  changes  to  a  liquid,  or  a  liquid  to  a  gas,  heat 
is  absorbed ;  and  conversely,  whenever  a  gas  is  liquefied,  or  a 
liquid  becomes  a  solid,  heat  is  evolved ;  although,  as  a  general 
rule,  this  change  of  state  is  accompanied  by  no  change  of  tem- 
perature. Thus,  one  kilogramme  of  ice,  in  melting,  absorbs 
79  units  of  heat,  although  the  temperature  remains  at  0°  dur- 
ing the  change ;  and  when,  by  boiling,  a  kilogramme  of  water 
is  converted  into  steam,  under  the  normal  pressure  of  the  air, 
no  less  than  537  units  of  heat  disappear,  although  the  tem- 
perature both  of  the  steam  and  of  the  water  is  constant  at  100° 
during  the  whole  period.  On  the  other  hand,  when  the  steam 
is  condensed  or  the  water  frozen,  absolutely  the  same  amount 
of  heat  is  set  free  as  was  before  absorbed.  The  heat  thus  ab- 
sorbed or  set  free  is  generally  called  the  latent  heat  of  the  liquid 
or  gas,  and  in  the  case  of  many  substances  the  amount  has 
been  carefully  measured.  Chem.  Phys.  (277)  and  (299).  Ac- 
cording to  the  theory  we  are  studying,  these  effects  are  the 
direct  results  of  the  molecular  condition  of  matter.  The  change 
of  state  must  be  accompanied  by  a  change  in  the  relative  position 
of  the  molecules,  or  in  their  distance  from  each  other ;  and  this 
change,  in  its  turn,  must  be  attended  with  a  destruction  or  pro- 
duction of  the  moving  power  on  which  the  effects  of  heat  de- 
pend. Chem.  Phys.  (215  bis.). 

15.  Sources  of  Heat.  —  The  sun  is  the  original  source  of 
almost  all  the  heat  we  enjoy  on  the  earth,  for  the  effect  of  the 
earth's  internal  heat,  at  its  surface,  is  at   best  very  small,  — 
and  all  our  artificial  sources  of  heat  have  drawn  their  supply 
either  directly  or  indirectly  from  the  great  central  luminary. 
According  to  our  theory  the  effect  of  the  sun's  rays  is  a  simple 
result  of  the  transfer  of  molecular  motion  from  the  sun  to 
the  earth,  either  by  some  unknown  influence  exerted  from  a 
distance,  or  else  by  an  actual  transfer  of  motion  through  the 
material  particles  of  the  ether,  which  is  assumed  to  fill  the  in- 
tervening space.    The  great  source  of  all  artificial  heat  is  com- 
bustion in  its  many  forms,  and  this,  as  we  shall  hereafter  see,  is 
merely  a  clashing  together  of  material  molecules,  and  is  neces- 
sarily attended  with  a  great  development  of  that  moving  power 
to  which  we  refer  all  thermal  effects. 

16.  Specific  Heat.  —  The  amount  of  heat  required  to  raise 


MOLECULES.  17 

to  the  same  extent  the  temperature  of  equal  weights  of  differ- 
ent substances  is  by  no  means  the  same.  The  quantity  is  capa- 
ble in  any  case  of  exact  measurement,  and  is  called  the  specific 
heat  of  the  substance.  The  amount  of  heat  required  to  raise  the 
temperature  of  one  kilogramme  of  water  one  centigrade  degree 
has  been  assumed  as  the  unit,  and  we  express  the  specific  heat 
of  other  substances  in  terms  of  this  measure.  Moreover,  since 
with  the  exception  of  hydrogen  the  specific  heat  of  water 
is  greater  than  that  of  any  substance  known,  the  specific  heat 
of  all  other  bodies  must  be  expressed  by  fractional  numbers. 
In  every  case,  unless  otherwise  stated,  the  numbers  indicate 
what  fraction  of  a  unit  of  heat  would  be  required  to  raise  the 
temperature  of  one  kilogramme  of  the  substance  from  0°  to  1° 
centigrade.  Chem.  Phys.  (232). 

17.  Molecular  Condition  of  Gases.  —  The  aeriform  state 
is  by  far  the  simplest  condition  of  matter,  and  there  are  two 
peculiarities  in  its  properties  which  lead  to  important  conclu- 
sions in  regard  to  its  molecular  conditions.  These  character- 
istics are  as  follows :  First,  All  true  gases  obey  the  same  law 
of  compressibility.  Secondly,  Equal  volumes  of  all  true  gases 
expand  equally  on  the  same  increase  of  temperature.  Chem. 
Phys.  (262).  Now,  according  to  the  mechanical  theory  of 
heat  (§  10)  these  peculiar  relations  of  the  aeriform  condition 
of  matter  are  best  explained  on  the  assumption  that  Equal 
volumes  of  all  gases  contain  the  same  number  of  molecules; 
and  since,  moreover,  this  theoretical  deduction  harmonizes 
with  almost  all  the  facts  of  chemistry,  it  has  been  universally 
adopted  as  a  fundamental  principle  of  the  science.  This 
peculiar  molecular  condition,  however,  is  only  found  in  the  gas, 
for  it  is  only  in  this  state  that  the  molecules  are  sufficiently 
separated  from  each  other  to  be  freed  from  the  mutual  action 
of  those  molecular  forces  which  give  rise  to  far  more  com- 
plicated relations  in  both  liquid  and  solid  bodies.  Moreover, 
with  our  ordinary  gases  (in  the  degree  of  condensation  in 
which  they  exist  under  the  pressure  of  the  atmosphere),  the 
molecules  are  not  yet  sufficiently  far  apart  to  be  wholly  freed 
from  the  effects  of  their  mutual  action,  and  hence  the  theo- 
retical condition  is  not  absolutely  fulfilled  ;  and  in  vapors, 
where  the  molecules  are  still  closer  together,  the  variation 
from  the  theory  is  quite  large.  In  proportion  as  the  gas  ex- 
2 


18  MOLECULES. 

pands,  the  theoretical  condition  is  approached,  and,  when  in  a 
state  of  great  expansion,  equal  volumes  of  all  gases  would 
undoubtedly  contain  exactly  the  same  number  of  molecules.  It 
is  only  then  that  we  reach  the  condition  of  what  we  have  called 
above  the  true  gas,  and  this  is  our  criterion  of  its  state,  —  that 
it  obeys  absolutely  the  law  of  Mariotte.  A  very  important 
corollary  follows  at  once  from  the  principle  we  have  just  de- 
duced. 

The  molecular  weight  of  all  substances  is  directly  propor- 
tioned to  their  specific  gravities  in  the  state  of  gas. 

We  have  adopted  in  this  book  hydrogen  gas  as  our  unit  of 
specific  gravity  for  aeriform  substances,  and  were  we  also  to  take 
the  molecule  of  hydrogen  as  our  unit  of  molecular  weight,  then 
the  number  which  expresses  the  specific  gravity  of  a  gas  would 
express  also  its  molecular  weight.  But  for  reasons  which  will 
appear  hereafter,  we  have  selected  the  half  hydrogen  molecule 
as  our  unit,  and  hence  the  molecular  weight  of  any  substance 
in  terms  of  this  unit  is  always  twice  its  specific  gravity  in  the 
state  of  gas.  In  Table  III.  we  have  given,  according  to  the 
most  accurate  experimental  data,  the  Sp.  Gr.  (referred  to 
hydrogen)  of  all  the  best  known  gases  and  vapors,  and  in  a 
parallel  column  we  have  also  given  the  Half-molecular  Weights 
of  the  same  substances  determined  by  chemical  analysis,  in  a 
manner  which  will  be  hereafter  described.  It  will  be  seen 
that  the  numbers  in  the  second  column  are  almost  precisely 
the  same  as  those  in  the  first,  and  the  slight  differences 
which  will  be  noticed,  either  arise  from  the  fact  that  the 
vapors,  under  the  conditions  in  which  alone  their  Sp.  Gr. 
can  be  accurately  determined,  are  not  true  gases,  that  is,  do 
not  exactly  obey  Mariotte's  law ;  or  in  other  cases,  where 
the  differences  are  more  considerable,  may  be  referred  to  a 
partial  decomposition  of  the  substance  itself  in  the  process  of 
the  experiment.  In  solving  the  problems  of  this  book,  and 
generally  in  most  chemical  problems,  the  Half-molecular  weight 
may  be  taken  as  the  true  Sp.  Gr.  The  logarithms  of  these 
values  given  in  the  last  column  of  the  table  will  be  found  useful 
in  this  connection.  Although  only  given  to  four  places  of 
decimals,  they  exceed  in  accuracy  the  experimental  data.  The 
values  in  the  column  of  0p.  (J$£.  referred  to  air,  are  given,  as 
a  rule,  to  one  decimal  place  beyond  the  limit  of  error. 


MOLECULES.  19 

Questions  and  Problems. 

1.  Are  the  qualities  of  a  molecule  of  any  substance,  the  same  as 
those  which  distinguish  the  substance  itself? 

2.  What  is  the  distinction  between  cohesion  and  adhesion  ? 

3.  When  the  barometer  stands  at  76  c.  m.,  with  what  weight  in 
grammes  is  the  air  pressing  against  each  square  centimetre  of  sur- 
face?    Sp.  Gr.  of  mercury  13.596.  Ans.  1033. 

4.  To  what  difference  of  pressure  does  a  difference  of  one  centi- 
metre in  the  barometric  column  correspond  ? 

Ans.  13.596  grammes. 

5.  When  a  mercury  barometer  stands  at  76  c.  m*.  how  high  would 
a  water  barometer  stand  ?     Also,  how  high  would  barometers  stand 
filled  with  alcohol  or  sulphuric  acid,  disregarding  in  each  case  the 
tension  of  the  vapor?    Sp.  Gr.  of  alcohol  0.81 ;  Sp.  Gr.  of  sulphuric 
acid  1.85.  Ans.  1033;  1275  and  558.2  c.  m. 

6.  A  volume  of  hydrogen  gas  was  found  to  be  200  c.  m.3     The 
height  of  the  barometer  observed  at  the  same  time,  was  74  c.  m. 
What  would  have  been  the  volume  if  observed  when  the  barometer 
stood  at  76  c.  m.  Ans.  194.7  cTm:3 

7.  A  volume  of  nitrogen  standing  in  a  bell-glass  over  a  mercury 
pneumatic  trough  measured  250  cTm".8     The  barometer  at  the  time 
stood  at  75.4  c.  m.,  and  the  level  of  the  mercury  in  the  bell  wa? 
found  by  measurement  to  be  6.5  above  the  surface  of  the  mercury 
in  the  trough.    Required  to  reduce  the  volume  to  standard  pressure. 

Ans.  The  pressure  of  the  air  on  the  surface  of  the  mercury  in  the 
trough  (measured  at  75.4  c.  m.)  was  balanced  first  by  the 
column  of  mercury  in  the  bell,  and  secondly  by  the  tension 
of  the  confined  gas.  Hence  the  pressure  to  which  the  gas 
was  exposed  was  equal  to  75.4  —  6.5  =  68.9  c.  m.  and  we 
have  76  :  68.9  =  250  :  x  =  226.7  cTnT:8 

8.  What  would  be  the  answer  to  the  same  problem,  had  the 
trough  been  filled  with  water  ? 

Ans.  The  water  column  in  the  bell  exerts  a  pressure  which  is  as 
much  less  than  the  pressure  of  the  mercury  column  in  the 
previous  problem,  as  the  Sp.  Gr.  of  water  is  less  than  the 
Sp.  Gr.  of  mercury.  Hence  we  have  13.6  :  1  =  6.5  :  0.48, 
also  75.4  —  0.48  =  74.92,  and  76  :  74,92  =  250  :  x  =  246.4 
cTm:8 

9.  A  closed  vessel,  which  displaces  one  litre  of  air,  is  poised  on  a 
balance  with  weights,  whose  volume  is  inconsiderable  when  com- 
pared with  that  of  the  vessel.     The  balance  is  in  equilibrium  when 


20  MOLECULES. 

the  barometer  stands  at  76  c.  m.     If  the  barometer  falls  to  71  c.  m. 
how  much  weight  must  be  added  to  restore  the  equilibrium  ? 

Ans.  85  milligrammes. 

10.  Given  the  weight  of  one  litre  of  dry  air  under  the  normal 
conditions  as  14.42  criths,  what  will  be  the  weight  of  one  litre  of 
dry  air  at  the  normal  temperature,  but  under  a  pressure  of  72  c.  m.  ? 

Ans.  13.67  criths. 

11.  A  volume  of  gas  measures  500  c.  m.3  at  15°  what  will  be  its 
volume  at  288°. 2  ?     In  this  and  the  next  three  problems  the  pressure 
is  assumed  to  be  constant.  Ans.  1000  cHS:3 

12.  To  what  Jemperature  must  an  open  vessel  be  heated  before 
one  quarter  of  the  air  which  it  contains  at  0°  is  driven  out  ? 

Ans.  9P.07. 

13.  An  open  vessel  is  heated  to  819°.6.     What  portion  of  the  air 
which  the  vessel  contained  at  0°  remains  in  it  at  this  temperature  ? 

Ans.  ^. 

14.  A  closed  glass  vessel,  which  at  13°  was  filled  with  air  having 
a  tension  of  76  c.  m.  is  heated  to  559°.4.     Determine  the  tension  of 
the  heated  air.  Ans.  3  atmospheres. 

15.  Reduce  the  following  volumes  of  gas  measured  at  the  tem- 
peratures and  pressure  annexed  to  0°  and  76  c.  m. 

1.  140   cTm.3       H=57c.  m.       t  =  136°.6       Ans.  70  cTni.3 

2.  320   cTW       #=95c.  m.       t=    91°.l     Ans.  300  cTm.3 

3.  480  .c~m;3       H=38c.  m.       *=    68°.3     Ans.  192  cTm.3 

16.  What  is  the  weight  of  dry  air  contained  in  a  glass  globe  of 
€40  cTTS:3  capacity  at  the  temperature  546°.4  and  under  a  pressure 
of  71.25  c.  m.  Ans.  0.2583  grammes. 

General  Solution.  —  In  order  to  make  the  solution  general  we 
will  represent  the  capacity  of  the  globe,  the  temperature  and  the 
height  of  the  barometer  by  V,  t  and  H  respectively.  We  can  also 
easily  find  from  Table  III.  that  one  cubic  centimetre  of  dry  air  at 
0°,  and  when  the  barometer  stands  at  76  c.  m.,  weighs  14.42  criths 
or  0.001292  grammes.  To  find  what  one  cubic  centimetre  would 
weigh  when  the  barometer  stands  at  H  centimetres,  we  make  use 
of  proportion  [6],  whence  we  derive 

w  =  0.001292  .  5, 

the  weight  of  one  cubic  centimetre  at  0°  and  under  a  pressure  of 
H  centimetres.     To  find  what  one  cubic  centimetre  would  weigh 


MOLECULES.  21 

under  the  same  pressure  but  at  t°,  it  must  be  remembered  that  one 
cubic  centimetre  at  0°  becomes  (1  -f-  t  0.00366)  cubic  centimetres 
at  t°  [7]  ;  therefore  at  t°  and  at  H  centimetres  of  the  barometer 
(1  -f-  t  0.00366)  67W  weigh  0.00129  .  3  grammes.  By  equating 
these  two  terms  we  obtain 


whence . 


(1  +  *  0.00366)':=  0.00129  .  5 

76 

1  —  0.00129  — - — 

'  1  -{-t 0.00366  *  76* 


the  weight  of  one  cubic  centimetre  at  t  °  and  under  a  pressure  of 
H  centimetres.     The  weight  of  Y  cubic  centimetres  (w)  is  evidently 


Thus  far  in  this  solution  we  have  neglected  the  cha'nge  in  capacity 
of  the  glass  globe  due  to  the  change  of  temperature.  This  causes 
no  sensible  error  when  the  change  of  temperature  is  small,  but 
when  the  change  of  temperature  is  quite  large  the  change  of  ca- 
pacity of  the  globe  must  be  considered.  If  the  capacity  is  Y  c.  m.3 
at  0°  it  becomes  at  t°  V  (1  -f-  t  0.00003).  (See  Chem.  Phys. 
§§  241  -  244.)  Introducing  this  value  for  Y  into  the  above  equa- 
tions we  obtain 

„=  0.00129  V  (1  +  t  0.00003)  .  .      .  [10  J] 


1  7.  Required  a  general  method  for  determining  the  gtj.  (g>r.  of 
a  vapor. 

Solution.  —  The  specific  gravity  of  a  vapor  has  been  denned  as  its 
weight  compared  with  the  weight  of  the  same  volume  of  hydrogen 
gas  under  the  same  conditions  of  temperature  and  pressure,  but 
practically  it  is  most  convenient  to  determine  the  £m.  (!$£.  with 
reference  to  air,  and  subsequently  to  reduce  the  result  to  the 
hydrogen  standard. 

To  find,  then,  the  Sp.  (J$r.  of  a  vapor,  we  must  ascertain  the 
weight  of  a  known  volume,  Y,  at  a  known  temperature,  t,  and  under 
a  known  pressure,  H,  and  divide  this  by  the  weight  of  the  same 
volume  of  air  at  the  same  temperature,  and  under  the  same  pressure. 
The  method  may  best  be  explained  by  an  example.  Suppose, 
then,  that  we  wish  to  ascertain  the  £j;n  ({$£.  of  alcohol  vapor. 
We  take  a  light  glass  globe  having  a  capacity  of  from  400  to  500 
cTliT.3,  and  draw  the  neck  out  in  the  flame  of  a  blast  lamp,  so  as  to 
leave  only  a  fine  opening,  as  shown  in  the  figure  at  a.  The  first 


22 


MOLECULES. 


step  is  now  to  ascertain  the  weight  of  the  glass  globe  when  com- 
pletely exhausted  of  air.     As  this  cannot  readily  be  done  directly, 

we  weigh  the  globe  full  of  air,  and 
then  subtract  the  weight  of  the  air, 
ascertained  by  calculation  from  the 
capacity  of  the  globe,  and  from  the 
temperature  and  pressure  of  the 
air,  by  means  of  equation  (10  a). 
Call  the  weight  of  the  globe  and  air 
W,  and  the  weight  of  the  air  10,  then 
W  —  w  is  the  weight  of  the  globe 
exhausted  of  air.  The  second  step 
is  to  ascertain  the  weight  of  the 
globe  filled  with  alcohol  vapor  at 
a  known  temperature,  and  under  a 
known  pressure.  For  this  purpose 
we  introduce  into  the  globe  a  few 
grammes  of  pure  alcohol,  and  mount  it  on  the  support  represented 
in  the  accompanying  figure.  By  loosening  the  screw,  r,  we  next 
sink  the  balloon  beneath  the  oil  contained  in  the  iron  vessel,  V,  and 
secure  it  in  this  position.  We  now  slowly  raise  the  temperature  of 
the  oil  to  between  300°  and  400°,  which  we  observe  by  means  of  the 
thermometer,  T.  The  alcohol  changes  to  vapor,  and  drives  out  the 
air,  which,  with  the  excess  of  vapor,  escapes  at  a.  When  the  bath 
has  attained  the  requisite  temperature,  we  close  the  opening  a,  by 
suddenly  melting  the  end  of  the  tube  at  a  with  a  mouth  blowpipe, 
and  as  nearly  as  possible  at  the  same  moment  observe  the  tempera- 
ture of  the  bath  and  the  height  of  the  barometer.  We  have  now 
the  globe  filled  with  alcohol  vapor  at  a  known  temperature,  and 
under  a  known  pressure.  Since  it  is  hermetically  sealed,  its  weight 
cannot  change,  and  we  can  therefore  allow  it  to  cool,  clean  it,  and 
weigh  it  at  our  leisure.  This  will  give  us  the  weight  of  the  globe 
filled  with  alcohol  vapor  at  a  known  temperature,  Z',  and  under  a 
known  pressure,  H'.  Call  this  weight  W.  The  weight  of  the 
vapor  is  W'  —  W  -f-  w.  The  third  step  is  to  ascertain  the  weight 
of  the  same  volume  of  air  at  the  same  temperature  and  under  the 
same  pressure.  This  can  easily  be  found  by  calculation  from  equa- 
tion (10  &).  The  last  step  is  to  find  the  capacity  of  the  globe,  which, 
although  we  have  supposed  it  known,  is  not  actually  ascertained 
experimentally  until  the  end  of  the  process.  For  this  purpose  we 
break  off  the  tip  of  the  tube  (a),  under  mercury,  which,  if  the  ex- 
periment has  been  carefully  conducted,  rushes  in  and  fills  the  globe 
completely.  We  then  empty  this  mercury  into  a  carefully  gradu- 
ated glass  cylinder,  and  read  off  the  volume.  We  find  then  the 


MOLECULES.  23 

Gp.  (!5t.  by  dividing  the  weight  of  the  vapor  by  the  weight  of  the 
au-.     The  formulas  for  the  calculation  are  then 

Weight  of  the  globe  and  air,  W. 

«  "      air,  w  =  0.001292  V  . L- 

1  +  t  0.00366     76 

"  "      globe  exhausted  of  air,  W  —  w. 

"  "         **      filled  with  vapor  at  a  temperature  t'  and 

under  a  pressure  H',  W'. 

"  "      vapor,  W'  —  W  -f  w. 

"  "      air  at  t'  and  under  a  pressure  H',  = 

0.001292  V  (1  -f  t  0.00003)  .  — 

W  —  W  +  w 


0.001292  V  (1+  t'  0.00003)  .  ^^  .  «' 


1.  Ascertain  the  Qyf  ^^.  of  alcohol  vapor  from  the  following 
data :  — 

Weight  of  glass  globe,  W         50.804  grammes. 

Height  of  barometer,  H           74.75  centimetres. 

Temperature,  t           18° 

Weight  of  globe  and  vapor,  W        50.824  grammes. 

Height  of  barometer,  H'         74.76  centimetres. 

Temperature,  t'           167° 

Volume,  V          35 1.5  cubic  centimetres. 

Ans.  1.575. 

2.  Ascertain  the  Pm    (£H)£.  of  camphor  vapor  from  the  following 
data :  — 

Weight  of  glass  globe,  W         50.134  grammes. 

Height  of  barometer,  H          74.2  centimetres. 

Temperature,  t           13°.5 

Weight  of  globe  and  vapor,  W'         50.842  grammes. 

Height  of  barometer,  H'         74.2  centimetres. 

Temperature,  {'           244° 

Volume,  V          295  cubic  centimetres. 

Ans.  5.371. 


CHAPTER    IV. 

ATOMS. 

18.  Definition.  —  The  atomic  theory  assumes  that  so  long 
as  the  identity  of  a  substance  is  preserved  its  molecules  remain 
undivided  ;  but  when,  by  some  chemical  change,  its  identity  is 
lost,  and  new  substances  are  formed,  the  theory  supposes  that  the 
molecules  themselves  are  broken  up  into  still  smaller  particles, 
which  it  calls  atoms.  Indeed  it  regards  this  division  of  the 
molecules  as  the  very  essence  of  a  chemical  change. 

The  word  atom  is  derived  from  a,  privative,  and  re/mo  (I 
cut),  and  recalls  a  famous  controversy  in  regard  to  the  infinite 
divisibility  of  matter,  which  for  many  centuries  divided  the 
philosophers  of  the  world.  But  chemistry  does  not  deal  with 
this  metaphysical  question.  It  asserts  nothing  in  regard  to  the 
possible  divisibility  of  matter ;  but  its  modern  theories  claim 
that,  practically,  this  division  cannot  be  carried  beyond  a  certain 
extent,  and  that  we  then  reach  particles  which  cannot  be  fur- 
ther divided  by  any  chemical  process  now  known.  These  are 
the  chemical  atoms,  and  the  atom  is  simply  the  unit  of  the 
chemist,  just  as  the  molecule  is  the  unit  of  the  physicist,  or  the 
stars  the  units  of  the  astronomer.  The  molecule  is  a  group  of 
atoms,  and  is  a  unit  in  the  microcosm,  of  which  it  is  a  part,  in 
the  same  sense  that  the  solar  system  is  a  unit  in  the  great  stel- 
lar universe.  The  molecule  has  been  defined  as  the  smallest 
particle  of  any  substance  which  can  exist  by  itself,  and  the 
atom  may  be  now  defined  as  the  smallest  mass  of  an  element 
that  exists  in  any  molecule. 

When  a  molecule  breaks  up,  it  is  not  supposed  that  the  atoms 
fall  apart  like  grains  of  sand ;  but  simply  that  they  arrange 
themselves  in  new  groups,  and  thus  give  rise  to  the  formation 
of  new  substances.  Indeed,  as  a  rule,  the  atoms  cannot  exist 
in  a  free  state,  and  with  few  exceptions  every  molecule  consists 
of  at  least  two  atoms.  This  is  thought  to  be  true,  even  of  the 
chemical  elements.  The  difference  between  the  molecules  of 


ATOMS.  25 

an  elementary  substance  and  those  of  a  compound,  according 
to  the  theory,  is  merely  this,  that  while  the  first  are  formed  by 
the  union  of  atoms  of  the  same  kind,  the  last  comprise  atoms 
of  different  kinds.  The  molecules  of  oxygen  gas  are  atomic 
aggregates  as  well  as  those  of  water,  only  the  molecules  of 
oxygen  consist  of  oxygen  atoms  alone,  while  the  molecules  of 
water  contain  both  oxygen  and  hydrogen  atoms.  Such  at  least 
is  the  constitution  of  most  elementary  substances.  Nevertheless, 
in  the  case  of  mercury,  zinc,  cadmium,  and  some  other  me- 
tallic elements,  the  facts  compel  us  to  believe  that  the  molecule 
consists  of  but  one  atom,  or,  in  other  words,  that  in  these  cases 
the  molecule  and  the  atom  are  the  same. 

19.  Atomic  Weights.  —  There  must  be  evidently  as  many 
kinds  of  atoms  as  there  are  elementary  substances ;  and,  since 
these  substances  always  unite  in  definite  proportions,  it  must 
be  also  true  that  the  elementary  atoms  have  definite  weights. 
This  once  assumed,  the  law  of  multiple  proportions,  as  well 
as  that  of  definite  proportions,  becomes  an  essential  part  of  our 
atomic  theory ;  for,  since  the  atoms  are  by  definition  indivis- 
ible, the  elements  can  only  combine  atom  by  atom,  and  must 
therefore  unite  either  in  the  proportion  of  the  atomic  weights 
or  in  some  simple  multiples  of  this  proportion.  We  have  dis- 
covered no  means  of  measuring  even  approximately  the  ab- 
solute weight  of  an  atom  ;  but,  after  we  have  determined,  from 
considerations  hereafter  to  be  discussed,  what  must  be  the  num- 
ber of  atoms  of  each  kind  in  one  molecule  of  any  substance, 
we  can  easily  calculate  their  relative  weight  from  the  results  of 
analysis.  A  few  examples  will  make  the  method  plain. 

1.  The  analysis  of  water,  given  on  page  6,  proves  that  in 
100  parts   it   contains  11.112   [farts  of  hydrogen  and  88.888 
parts  of  oxygen.    Every  molecule  of  water,  then,  must  contain 
these  two  elements  in  just  these  proportions.     Now  we  have 
good   reason  for   believing  that  each  molecule  of  water  is  a 
group  of  three  atoms,  —  two  of  hydrogen  and  one  of  oxygen. 
Then,  since  £  (11.112)  :  88.888  =  1  :  16,  it  follows  that  the 
oxygen  atom  must  weigh  16  times  as  much  as  the  hydrogen 
atom  ;  and,  if  we  make  the  hydrogen  atom  the  uni.t  of  our  atom- 
ic weight,  then  the  weight  of  the  oxygen  atom,  estimated  in 
these  units,  must  be  16. 

2.  The  analysis  of  hydrochloric  acid  gas  proves  that  it  con- 


given  in  Table  II.  These  numbers  are  the  mm 
of  chemical  science,  and  the  basis  of  almost  all  the  numerical 
calculations  which  the  chemist  has  to  make.  The  elements  of 
a  compound  body  are  always  united  either  in  the  proportions, 
by  weight,  expressed  by  the^e  numbers,  or  else  in  some  simple 
multiples  of  these  proportions ;  and  whenever,  by  the  breaking 
up  of  a  complex  compound,  or  by  the  mutual  action  of  different 
substances  on  each  other,  the  elements  rearrange  themselves, 
and  new  compounds  are  formed,  the  same  numerical  propor- 
tions are  always  preserved. 

The  atomic  weights  evidently  rest  on  two  distinct  kinds  of 
data ;  Jirst,  on  the  results  of  chemical  analysis,  which  are  facts 
of  observation,  and  in  regard  to  which  the  only  question  can  be 
as  to  their  greater  or  less  accuracy  ;  secondly,  on  our  conclu- 
sions in  regard  to  the  number  of  atoms  in  each  molecule  of  the 
substance  analyzed.  This  conclusion  again  is  based  chiefly  on 
two  classes  of  facts,  whose  bearing  on  the  subject  we  must 
briefly  consider. 

L  In  the  first  place  we  carefully  compare  together  all  the 
compounds  of  the  element  we  are  studying,  with  the  view  of 
discovering  the  smallest  weight  of  it  which  enters  into  the  com- 
position of  any  known  molecule ;  for  this  must  evidently  be  the 
atomic  weight  of  the  element.  An  example  will  make  the 
course  of  reasoning  intelligible. 

In  the  following  table  we  have  a  list  of  a  number  of  the 
most  important  compounds  containing  hydrogen,  all  of  which 
either  are  gases,  or  can  easily  be  changed  into  vapor  by  heat, 


ATOMS.  27 

so  that  their  specific  gravities  in  the  state  of  gas  can  be  readily 
determined.  From  these  specific  gravities  we  learn  the  weights 
of  the  molecules  (compare  §  17)  which  are  given  in  the  second 
column  of  the  table.  In  the  third  column  we  have  given  the 
weight  of  hydrogen  contained  in  the  molecules,  referred,  of 
course,  to  the  same  unit  as  the  weight  of  the  molecules 
themselves :  — 

Weight  of  Molecule 

referred  to  Weight  of  Hydrogen 

Compounds  of  Hydrogen.  Hydrogen  Atom.  in  the  Molecule. 

Hydrochloric  Acid  36.5  1 

Hydrobromic  Acid  81.0  1 

Hydriodic  Acid  128.0  1 

Hydrocyanic  Acid  27.0  1 

Hydrogen  Gas  2,0  2 

Water  18.0  2 

Sulphuretted  Hydrogen  34.0  2 

Seleniuretted  Hydrogen  81.5  2 

Formic  Acid  46.0  2 

Ammonia  1 7.0  3 

Phosphuretted  Hydrogen  34.0  3 

Arseniuretted  Hydrogen  78.0  3 

Acetic  Acid  60.0  4 

Olefiant  Gas  28.0  4 

Marsh  Gas  16.0  4 

Alcohol  46.0  6 

Ether  74.0  10 

Assuming  now,  as  has  been  assumed  in  this  table,  that  a 
molecule  of  hydrogen  gas  weighs  2,  it  appears  that  the 
smallest  mass  of  hydrogen  which  the  molecule  of  any  known 
substance  contains,  weighs  jtist  one  half  as  much,  or  1.  We 
infer,  therefore,  that  this  mass  of  hydrogen  cannot  be  divided 
by  any  chemical  means,  or,  in  other  words,  that  it  is  the  hydro- 
gen atom.  The  molecule  of  hydrogen  gas  contains  then  two 
hydrogen  atoms,  and  this  atom  is  the  unit  to  which  we  refer  all 
molecular  and  atomic  weights. 

If  now,  in  like  manner,  we  bring  into  comparison  all  the 
volatile  compounds  of  oxygen,  we  shall  find  that  the  smallest 
mass  of  oxygen  which  exists  in  the  molecule  of  any  known 
substance  weighs  16,  —  the  atom  of  hydrogen  weighing  1, — 
and  hence  we  infer  that  this  mass  of  oxygen  is  the  oxygen  atom. 
Moreover  it  will  appear  that  a  molecule  of  oxygen  gas  weighs 


28  ATOMS. 

32,  and  hence  it  follows  that  each  molecule  of  oxygen  gas,  like 
the  molecule  of  hydrogen,  is  formed  by  the  union  of  two  atoms. 
A  similar  comparison  would  show  that,  while  the  molecule  of 
nitrogen  gas  weighs  28,  the  atom  weighs  14,  so  that  here  again 
the  molecule  consists  of  two  atoms.  This  method  of  investiga- 
tion can  be  extended  to  a  large  number  of  the  chemical  ele- 
ments, and  the  conclusions  to  which  it  leads  are  evidently  le- 
gitimate, and  cannot  be  set  aside,  until  it  can  be  shown  that 
some  substance  exists  whose  molecule  contains  a  smaller  mass 
of  any  element  than  that  hitherto  assumed  as  the  atomic  weight, 
or,  in  other  words,  until  the  old  atom  has  been  divided. 

2.  The  second  class  of  facts  on  which  we  rely  for  determin- 
ing the  number  of  atoms  in  a  given  molecule  is  based  on  the 
specific  heat  of  the  elements  (compare  §  16).  It  would  appear 
tHal'tlie  specific  heat  is  the  same  for  all  atoms,  and,  if  this  is 
true,  we  might  expect  that  equal  amounts  of  heat  would  raise 
to  the  same  extent  the  temperatures  of  such  quantities  of  the 
various  elementary  substances  as  contain  the  same  number  of 
atoms,  provided,  of  course,  that  these  atomic  aggregates  are 
compared  under  the  same  conditions.  Now  we  can  determine 
accurately  the  number  of  units  of  heat  required  to  raise  the 
temperature  of  equal  weights  of  the  elementary  substances  one 
degree,  and  the  results,  which  we  call  the  specific  heat  of  the 
elements,  are  given  in  works  on  physics.  Chem.  Phys.  (232). 
Evidently,  if  our  principle  is  true,  these  values  must  be  pro- 
portional in  every  case  to  the  number  of  atoms  of  each  element 
contained  in  the  equal  weights  compared.  Representing  then 
by  S  and  S'  the  specific  heat  of  two  elementary  substances,  by 
m  and  m)  the  weights  of  the  corresponding  atoms,  and  by  unity 
the  equal  weights  compared,  we  shall  have,  in  any  case, 

S:S'=  i:i,  OTmS=m'S',  [11] 

m    m9  L.    J 

that  is,  The  product  of  the  atomic  weight  of  an  elementary  sub- 
stance by  its  specific  heat  is  always  a  constant  quantity. 

Taking  now  the  atomic  weights  obtained  by  the  method  first 
given,  and  the  specific  heats  of  the  elements  as  they  have  been 
determined  by  experimenting  on  these  substances  in  the  solid 
state,  we  find  that,  with  only  three  exceptions,  our  inference  is 


ATOMS.  29 

correct ;  and  this  principle  not  only  frequently  enables  us  to  fix 
the  atomic  weight  of  an  element,  when  the  first  method  fails, 
but  it  also  serves  to  corroborate  the  general  accuracy  of  our 
results.  It  is  true,  owing  undoubtedly  to  many  causes  which 
influence  the  thermal  conditions  of  a  solid  body,  that  this  prod- 
uct is  not  absolutely  constant.  It  varies  between  5.7  and  6.9, 
the  most  probable  value  being  very  nearly  6.34.  But  the 
variation  is  riot  important,  so  far  as  the  determination  of  the 
atomic  weights  is  concerned.  This  determination,  as  we  have 
seen,  rests  chiefly  on  the  results  of  analysis.  The  question  al- 
ways is  only  between  two  or  three  possible  hypotheses,  and  as 
between  these  the  specific  heat  will  decide.  For  example,  an 
analysis  of  chloride  of  silver  proves  that  each  molecule  contains 
for  one  atom,  or  35.5  parts  of  chlorine,  108  parts  of  silver. 
Now,  108  parts  of  silver  may  represent  one7two,  three,  or  four 
atoms,  or  it  may  be  that  this  quantity  only  represents  a  fraction 
of  an  atom.  To  determine,  we  divide  6.34  by  0.057,  the  specific 
heat  of  silver.  The  result  is  111,  which,  though  not  the  exact 
atomic  weight,  is  near  enough  to  show  that  108  is  the  weight 
of  one  atom,  and  not  of  two  or  three.  The  exceptions  to  this 
rule  referred  to  above  are  carbon,  boron,  and  silicon.  But  the 
specific  heat  of  these  elements  varies  so  very  greatly  with 
the  differences  of  physical  condition  —  the  so-called  allotropic 
modifications  —  which  these  elements  present,  —  Chem.  Phys. 
(234),  —  that  the  exceptions  are  not  regarded  as  invalidat- 
ing the  general  principle.  The  law  simply  fails  in  these  cases, 
and  we  can  see  why  it  fails. 

This  important  law,  whose  bearing  on  our  subject  we  have 
briefly  considered,  was  first  discovered  by  Dulong  and  Petit,  and 
was  subsequently  verified  by  the  very  careful  experiments  of 
Regnault.  More  recently  it  has  been  found,  by  Voestyn  and 
others,  that  its  application  extends,  in  some  cases  at  least,  to 
chemical  compounds ;  for  it  would  seem  that  the  atoms  retain, 
even  when  in  combination,  their  peculiar  relationsTto  heat,  so 
that  the  product  of  the  specific  heat  of  a  substance  by  its  molec- 
ular weight  is  equal  to  as  many  times  6.3  as  there  are  atoms  in 
the  molecule.  Thus  the  specific  heat  of  common  salt,  multiplied 
by  its  molecular  weight,  gives  0.214  X  58.5  =  12.52,  which  is 
very  nearly  equal  to  6.3  X  2  ;  while  in  the  case  of  corrosive 
sublimate  the  corresponding  product,  0.069  X  271  =  18.70,  is 


30  ATOMS. 

nearly  equal  to  6.3  X  3,  —  results  which  are  in  accordance 
with  our  views  in  regard  to  the  number  of  atoms  in  the  mole- 
cules of  these  substances. 

We  have  here,  then,  an  obvious  method  by  which  we  might 
determine  the  number  of  atoms  in  the  molecule  of  any  solid, 
and  which  would  be  of  the  very  greatest  value  in  investigating 
the  atomic  weights,  could  we  rely  on  the  general  application 
of  our  law.  We  do  not  expect  mathematical  exactness.  We 
know  very  well  that  the  specific  heat  of  solid  bodies  varies 
very  greatly  with  the  temperature,  as  well  as  from  other  phys- 
ical causes,  and  that  it  is  impossible  to  compare  them  under 
precisely  the  same  conditions,  as  would  be  required  in  order  to 
secure  accuracy.  But,  unfortunately,  the  discrepancies  are  so 
great,  and  we  are  so  ignorant  of  their  cause,  that  as  yet  we 
have  not  been  able  to  place  much  reliance  on  the  specific  heat 
as  a  means  of  determining  the  number  of  atoms  in  the  mole- 
cules of  a  compound. 

3.  Lastly,  assuming  that  both  of  the  means  we  have  consid- 
ered fail  to  give  satisfactory  evidence  in  regard  to  the  number 
of  atoms  in  the  molecule  of  a  given  substance  (which  we  may 
have  analyzed  for  the  purpose  of  determining  some  atomic 
weight),  we  may  frequently,  nevertheless,  reach  a  satisfactory, 
or  at  least  a  probable  conclusion,  byjcomparing  the  substance 
we  are  investigating  with  some  closely  allied  substance  whos.e 
constitution  is  known.  Thus,  if  the  molecule  of  sodic  chlo- 
ride (common  salt)  contains  two  atoms,  it  is  probable  that 
the  molecules  of  sodic  iodide,  as  well  as  those  of  potassic 
chloride  and  potassic  iodide,  contain  the  same  number ;  for 
all  these  compounds  not  only  have  the  same  crystalline  form 
and  the  same  chemical  relations,  but  also  they  are  composed 
of  closely  allied  chemical  elements.  Nevertheless  it  is  true,  in 
very  many  cases,  that  our  conclusion  in  regard  to  the  number 
of  atoms  which  a  molecule  may  contain  is  more  or  less  hypo- 
thetical, and  hence  liable  to  error  and  subject  to  change.  This 
uncertainty,  moreover,  must  extend  to  the  atomic  weights  of 
the  elements,  so  far  as  they  rest  on  such  hypothetical  conclu- 
sions. 

If  we  change  the  hypothesis  in  any  case,  we  shall  obtain  a 
different  atomic  weight;  but  then  the  new  weight  will  be 


ATOMS.  31 

• 

some  simple  multiple  of  the  old,  and  will  not  alter  the  impor- 
tant relations  to  which  we  first  referred.  These  fundamental 
relations  are  independent  of  all  hypothesis,  and  rest  on  well- 
established  laws. 

The  atomic  weights  are  the  numerical  constants  of  chem- 
istry, and  in  determining  their  value  it  is  necessary  to  take 
that  care  which  their  importance  demands.  The  essential  part 
of  the  investigation  is  the  accurate  analysis  of  some  compound 
of  the  element  whose  atomic  weight  is  sought.  The  compound 
selected  for  the  purpose  must  fulfil  several  conditions.  It  must 
be  one  which  can  be  prepared  in  a  condition  of  absolute  purity. 
It  must  be  one  the  proportions  of  whose  constituents  can  be 
determined  with  the  greatest  accuracy  by  the  known  methods 
of  analytical  chemistry.  It  must  contain  a  second  element 
whose  atomic  weight  is  well  established.  Finally,  it  should  be 
a  compound  whose  molecular  condition  is  known,  and  it  is  best 
that  this  should  be  as  simple  as  possible.  When  they  are  once 
thus  accurately  determined,  the  atomic  weights  become  essen- 
tial data  in  all  quantitative  analytical  investigations. 

Questions  and  Problems. 

1.  Does  the  integrity  of  a  substance  reside  in  its  molecules  or  in 
its  atoms  ? 

2.  We  find  by  analysis  that  in  100  parts  of  potassic  chloride 
there  are   52.42  parts  of  potassium  and  47.58  parts  of  chlorine. 
Moreover,  we  know  from  previous  experiments  that  the  atomic 
weight  of  chlorine  is  35.5,  and  we  have  reason  to  believe  that  every 
molecule  of  the  compound  consists  of  two  atoms,  one  of  potassium 
and  one  of  chlorine.      What  is  the  atomic  weight  of  potassium  ? 

Ans.  39.1. 

3.  We  find  by  analysis  that  in  100  parts  of  phosphoric  anhydride 
there  are  43.66  parts  of  phosphorus  and  56.34  parts  of  oxygen. 
Moreover,  we  know  that  the  atomic  weight  of  oxygen  is  16 ;  and  we 
have  reason  to  believe  that  every  molecule  of  the  compound  consists 
of  seven  atoms,  2  of  phosphorus  and  5  of  oxygen.     What  is  the 
atomic  weight  of  phosphorus  ?  Ans.  31. 

4.  In  Table  III.  the  student  will  find  the  molecular  weights  of  the 
following  oxygen  compounds;  and  we  give  below,  following  the 
name,  the  weight  of  oxygen  (estimated  like  the  molecular  weight 
in  hydrogen  atoms)  which  each  contains.     From  these  data  it  is 


32  ATOMS. 

• 

required  to  determine  the  atomic  weight  of  oxygen.  Oxygen  Gas, 
32  ;  Water,  16  ;  Sulphurous  Anhydride,  32,  Sulphuric  Anhydride, 
48;  Phosphoric  Oxychloride,  16;  Carbonic  Oxide,  16;  Carbonic 
Anhydride,  32  ;  Osmic  Anhydride,  64  ;  Nitrous  Oxide,  16  ;  Nitric 
Oxide,  16  ;  and  Nitric  Peroxide,  32.  Ans.  16. 

5.  We  give  below  the  weight  of  chlorine  in  one  molecule  of 
several  of  its  most  characteristic  volatile  compounds.     It  is  required 
to  deduce  the  atomic  weight  of  chlorine  on  the  principle  of  the  last 
problem.      Chlorine  gas,  71;  Phosphorous  Chloride,  106.5;  Phos- 
phoric Oxychloride,  106.5;    Arsenious  Chloride,   106.5;    Phosgene 
Gas,  71  ;    Stannic  Chloride,  142  ;    Stanno-triethylic  Chloride,  35.5 ; 
and  Hydrochloric  Acid,  35.5.  Ans.  35.5. 

6.  Review  the  steps  of  the  reasoning  by  which  the  atomic  weights 
have  been  deduced  in  the  last  two  problems,  and  show  that  the 
"  molecular  weight "  and  "  the  weight  of  the  element  in  one  molecule  * 
are  actual  and  independent  experimental  data. 

7.  Analysis  shows  that  in  1 00  parts  of  mercuric  chloride  there  are 
73.80  parts  of  mercury  and  26.20  parts  of  chlorine.     The  specific 
heat  of  mercury  is  0.032.     What  is  the  probable  atomic  weight  of 
mercury,  that  of  chlorine  being  35.5  V     Also,  how  many  atoms  of 
each  element  does  one  molecule  of  the  compound  contain  ? 

Ans.  Atomic  weight  of  mercury,  200.      Each  molecule  consists 
of  one  atom  of  mercury  and  two  of  chlorine. 

8.  Analysis  shows  that  in  1 00  parts  of  ferric  oxide  there  are  70 
parts  of  iron  and  30  parts  of  oxygen.     The  specific  heat  of  iron  is 
0.114.     What  is  the  probable  atomic  weight  of  iron,  that  of  oxygen 
being  16?    and  also,  how  many  atoms  of  each  element  does  one 
molecule  of  the  oxide  contain  ? 

Ans.  Atomic  weight  of  iron,  56.     One  molecule  of  ferric  oxide 
contains  2  atoms  of  iron  and  3  of  oxygen. 

9.  The  molecular  weight  of  silicic  chloride  is  1 70,  and  its  specific 
heat,  0.1907.     How  many  atoms  does  one  molecule  of  the  compound 
probably  contain  ?  Ans.  5. 

10.  The  molecular  weight  of  mercuric   iodide  is  454,  and  its 
specific  heat,  0.042.     How  many  atoms  does  one  molecule  of  the 
compound  probably  contain  ?  Ans.  3. 


CHAPTER  V. 

CHEMICAL    NOTATION. 

20.  Chemical  Symbols.  —  The  atomic  theory  has  found  ex- 
pression in  chemistry  in  a  remarkable  system  of  notation,  which 
has  been  of  the  greatest  value  in  the  study  of  the  science.  In 
this  system,  the  initial  letter  of  the  Latin  name  of  an  element 
is  used  as  the  symbol  of  that  element,  and  represents  in  every 
case  one  atom.  Thus  0  stands  for  one  atom  of  Oxygen,  N  for 
one  atom  of  Nitrogen,  H  for  one  atom  of  Hydrogen.  When 
several  names  have  the  same  initial,  we  add  for  the  sake  of  dis- 
tinction a  second  letter.  Thus  O  stands  for  one  atom  of  Car- 
bon, Cl  for  one  atom  of  Chlorine,  Ca  for  one  atom  of  Calcium, 
Cu  for  one  atom  of  Cuprum  (copper),  Or  for  one  atom  of 
Chromium,  Co  for  one  atom  of  Cobalt,  Cd  for  one  atom  of 
Cadmium,  Cs  for  one  atom  of  Caesium,  and  Ce  for  one  atom 
of  Cerium.  The  symbols  of  all  the  elements  are  given  in 
Table  II.  Several  atoms  of  the  same  elq^kt  are  generally 
indicated  by  adding  figures,  but  distinguisKiqg  them  from  alge- 
braic exponents  by  placing  them  below  the  letters.  Thus  Sn2 
stands  for  two  atoms  of  Stannum  (tin),  S3  for  three  atoms 
of  Sulphur,  and  I5  for  five  atoms  of  Iodine.  Sometimes,  how- 
ever, in  order  to  indicate  certain  relations,  we  repeat  the  symbol 
with  or  without  a  dash  between  them,  thus  H-H  represents  a 
group  of  two  atoms  of  Hydrogen,  Se=Se  a  group  of  two  atoms 
of  Selenium.  We  can  now  easily  express  the  constitution  of 
the  molecule  of  any  substance  by  simply  grouping  together  the 
symbols  of  the  atoms  of  which  the  molecule  consists.  This 
group  is  generally  called  the  symbol  of  the  substance,  and 
stands  in  every  case  for  one  molecule.  Thus  NaCl  is  the  sym- 
bol of  common  salt,  and  represents  one  molecule  of  salt.  ff2  0 
is  the  symbol  of  water,  and  represents,  as  before,  one  molecule. 
So  in  like  manner  H%N  stands  for  one  molecule  of  ammonia 
gas,  H4  C  for  one  molecule  of  marsh  gas,  KNO^  for  one  mole- 
cule of  saltpetre,  H2SO^  for  one  molecule  of  sulphuric  acid, 
3 


34  CHEMICAL  NOTATION. 

O2N402  for  one  molecule  of  acetic  acid,  H-H  for  one 
molecule  of  hydrogen  gas.  We  do  not,  however,  always 
write  the  symbols  in  a  linear  form,  but  group  the  letters  in  such 
a  way  as  will  best  indicate  the  relations  we  are  studying. 
When  several  molecules  of  the  same  substance  take  part  in  a 
chemical  change,  we  represent  the  fact  by  writing  a  numerical 
coefficient  before  the  molecular  symbol.  A  figure  so  placed 
always  multiplies  the  whole  symbol.  Thus  &H-N03  stands 
for  four  molecules  of  nitric  acid,  3C2JH60  for  three  molecules 
of  alcohol,  600  for  six  molecules  of  oxygen  gas.  When 
clearness  requires  it,  we  enclose  the  symbol  of  the  molecule  in 
parentheses,  thus,  4(//3^),  or  (ffs=N)4.  The  precise  mean- 
ing of  the  dashes  will  hereafter  appear.  They  are  used,  like 
punctuation  marks,  to  point  off  the  parts  of  a  molecular  sym- 
bol, between  which  we  wish  to  distinguish. 

21.  Chemical  Reactions.  —  These  chemical  symbols  give  at 
once  a  simple  means  of  representing  all  chemical  changes.  As 
these  changes  almost  invariably  result  from  the  reaction  of  one 
substance  on  another,  they  are  called  Chemical  Reactions.  Such 
reactions  must  necessarily  take  place  between  molecules,  arid 
simply  consist  in  the  breaking  up  of  the  molecules  and  the  rear- 
rangement of  the  atoms  in  new  groups.  In  every  chemical  re- 
action we  must  distinguish  between  the  substances  which  are 
involved  in  the  change  and  those  which  are  produced  by  it. 
The  first  will  be  termed  the  factors  and  the  last  the  products  of 
the  reaction.  As  matter  is  indestructible,  it  follows  that  The 
sum  of  the  weights  of  the  products  of  any  reaction  must  always 
be  equal  to  the  sum  of  the  weights  of  the  factors,  and,  further, 
that  The  number  of  atoms  of  each  element  in  the  products  must 
be  the  same  as  the  number  of  atoms  of  the  same  kind  in  the 
factors.  This  statement  seems  at  first  sight  to  be  contradicted 
by  experience,  since  wood  and  many  other  combustibles  are 
consumed  by  burning.  In  all  such  cases,  however,  the  apparent 
annihilation  of  the  substance  arises  from  the  fact  that  the  prod- 
ucts of  the  change  are  invisible  gases ;  and,  when  these  are  col- 
lected, their  weight  is  found  to  be  equal,  not  only  to  that  of  the 
substance,  but  also,  in  addition,  to  the  weight  of  the  oxygen  from 
the  air  consumed  in  the  process.  As  the  products  and  factors 
of  every  chemical  change  must  be  equal,  it  follows  that  A 
chemical  reaction  may  always  be  represented  in  an  equation 


CHEMICAL  NOTATION.  35 

by  writing  the  symbols  of  the  factors  in  the  first  member  and 
those  of  the  products  in  the  second.  Thus,  the  following  equa- 
tion expresses  the  reaction  of  dilute  sulphuric  acid  on  zinc,  by 
which  hydrogen  gas  is  commonly  prepared.  The  products  are 
a  solution  of  zinc  sulphate  and  hydrogen  gas. 

Zn  +  (ff2S04  +  Aq)  =  (ZnSOt  +  Aq)  +  HHH.     [12] 

The  initial  letters  of  the  Latin  word  Aqua  are  here  used 
simply  to  indicate  that  the  substances  enclosed  with  it  in  pa- 
rentheses are  in  solution.  The  symbol  Zn  is  printed  in  "  full- 
faced  "  type  to  indicate  that  the  metal  is  used  in  the  reac- 
tion in  its  well-known  solid  condition  ;  while  the  symbol  of 
the  molecule  of  hydrogen  is  printed  in  skeleton  type  to  indi- 
cate the  condition  of  gas.  This  usage  will  be  followed  through- 
out the  book;  but,  generally,  when  it  is  not  important  to  indicate 
the  condition  of  the  materials  involved  in  the  reaction,  ordinary 
type  will  be  used.  The  molecule  of  hydrogen  gas  consists  of 
two  atoms,  as  our  reaction  indicates,  and  this  is  the  smallest 
quantity  of  hydrogen  which  can  either  enter  into  or  be  formed 
by  a  chemical  change.  The  molecule  of  zinc  is  known  to 
consist  of  only  one  atom.  When  the  molecular  constitution 
of  an  element  is  not  known,  we  simply  write  the  atomic  symbol 
in  the  reaction. 

Among  chemical  reactions  we  may  distinguish  at  least  three 
classes.  First,  Analytical  Reactions,  in  which  a  complex  mole- 
cule is  broken  up  into  simpler  ones.  Thus,  when  sodic  bisul- 
phate  is  heated,  it  breaks  up  into  sodic  sulphate  and  sulphuric 
anhydride,  — 

SOS.  [13] 


So,  also,  by  fermentation  grape  sugar  or  glucose  breaks  up  into 
alcohol  and  carbonic  anhydride,  — 

<76#12  06  =  2  C2ff6  0  +  2  C02.  [14] 

Secondly,  Synthetical  Reactions,  in  which  two  molecules 
unite  to  form  a  more  complex  group.  Thus  baryta  burns 
in  an  atmosphere  of  sulphuric  anhydride,  and  forms  baric 
sulphate,  — 

[15] 


36  CHEMICAL  NOTATION. 

In  like  manner  ammonia  enters  into  direct  union  with  hydro- 
chloric acid  to  form  ammonic  chloride,  — 

HJT  +  HCl  =  HJTCl  [16] 

Thirdly,  Metathetical  Reactions,  in  which  the  atoms  of  one 
molecultT  change  place  with  the  dissimilar  atoms  of  another, 
one  atom  of  one  molecule  replacing  one,  two,  three,  or  more 
atoms  of  the  other,  as  the  case  may  be.  Thus,  when  we  add  a 
solution  of  common  salt  to  a  solution  of  argentic  nitrate,  we  ob- 
tain a  white  precipitate  l  of  argentic  chloride,  while  sodic  nitrate 
remains  in  solution.  The  result  is  obtained  by  a  simple  in- 
terchange between  an  atom  of  silver  and  an  atom  of  sodium, 
as  the  following  reaction  shows :  — 

(Na  Cl+  AgNO,  +  Ag)  =  (NaNO,  +  Aq)  +  AgCl.    [17] 

In  the  next  example,  one  atom  of  barium  changes  place  with 
two  atoms  of  hydrogen.  Baric  chloride  and  sulphuric  acid 
yield  hydrochloric  acid  and  insoluble  baric  sulphate,  which 'is 
precipitated  from  the  solution  in  water  as  the  reaction  in- 
dicates, — 

(Sa  C12  +  ff2S04  +  Ag)  =  (ZHCI  +  Aq)  +  BaSO4.    [18] 

Of  the  three  classes  of  chemical  reactions  the  last  is  by  far 
the  most  common,  and  many  chemical  changes  which  were  for- 
merly supposed  to  be  examples  of  simple  analysis  or  synthesis 
are  now  known  to  be  the  results  of  metathesis.  In  very  many 
cases,  however,  a  chemical  reaction  cannot  be  explained  in 
either  of  these  ways  alone,  but  seems  to  consist  in  a  primary 
union  of  two  or  more  molecules  and  a  subsequent  splitting  up 
of  this  large  group.  Indeed,  this  is  the  best  way  of  conceiving 
of  all  metathetical  reactions,  for  we  do  not  suppose  that  in  any 
case  there  is  an  actual  transfer  of  atoms  from  one  molecule  to 
the  other.  The  word  metathesis  is  merely  used  to  indicate  the 
result  of  the  process,  not  the  manner  in  which  the  change  takes 
place,  and  the  same  is  true  of  the  words  analysis  and  synthesis. 

1  The  separation  of  a  solid  or  sometimes  of  a  liquid  substance  in  a  fluid 
menstruum,  as  the  result  of  a  chemical  reaction,  is  called  precipitation,  and 
the  material  which  separates,  a  precipitate ;  and  this,  too,  even  when  the  ma- 
terial, being  lighter  than  the  fluid,  rises  instead  of  falls. 


CHEMICAL  NOTATION.  37 

The  common  method  of  preparing  carbonic  anhydride  is  to 
pour  a  solution  of  hydrochloric  acid  on  small  lumps  of  marble 
(calcic  carbonate),  — 


CaC03  +  (2ffCl  +  Ag)  =  (  Ca  CO,  H,  C12  +     [19] 
Aq)  =  (OaCl2  +  H.,0  -f  Aq)  + 


We  may  suppose  that  the  molecules  of  the  two  substances  are, 
in  the  first  place,  drawn  together  by  the  force  which  manifests 
itself  in  the  phenomena  of  adhesion,1  but  that,  as  they  approach, 
a  mutual  attraction  between  their  respective  atoms  comes  into 
play,  which,  the  moment  the  molecules  come  into  collision, 
causes  the  atoms  to  arrange  themselves  in  new  groups.  The 
groups  which  then  result  are  determined  by  many  causes 
whose  action  can  seldom  be  fully  traced  ;  but  there  are  two 
conditions  which,  when  the  substances  are  in  solution,  have  a 
very  important  influence  on  the  result.  These  conditions  may 
be  thus  stated  :  — 

1.  Whenever  a  compound  can  be  formed,  which  is  insoluble 
in  the  menstruum  present,  this  compound  always  separates  as 
a  precipitate. 

2.  Whenever  a  gas  can  be  formed,  or  any  substance  which 
is  volatile  at  the  temperature  at  which  the  experiment  is  made, 
this  volatile  product  is  set  free. 

The  reactions  17  and  18  of  this  section  are  examples  of 
the  first,  while  the  reactions  12  and  19  are  examples  of  the 
second  of  these  conditions.  The  facts  just  stated  illustrate 
an  important  truth,  which  must  be  carefully  borne  in  mind  in 
the  study  of  chemistry.  A  chemical  equation  differs  essen- 
tially from  an  algebraic  expression.  Any  inference  which 
can  be  legitimately  drawn  from  an  algebraic  equation  must,  in 
some  sense,  be  true.  It  is  not  so,  however,  with  chemical  sym- 
bols. These  are  simply  expressions  of  observed  facts,  and, 
although  important  inferences  may  sometimes  be  drawn  from 
the  mere  form  of  the  expression,  yet  they  are  of  no  value 
whatever  unless  confirmed  by  experiment.  Moreover,  the  facts 

1  We  find  it  convenient  to  distinguish  between  the  force  which  holds  to- 
gether different  molecules  and  that  which  unites  the  atoms  of  the  molecules. 
To  the  last  we  give  the  name  of  chemical  affinity,  while  we  call  the  first  co- 
hesion or  adhesion,  according  as  it  is  exerted  between  molecules  of  the  same 
kind  or  those  of  a  different  kind. 


38  CHEMICAL  NOTATION. 

which  are  expressed  in  this  peculiar  system  of  notation  are 
as  purely  materials  for  the  memory  as  if  they  were  described 
in  common  language. 

22.  Compound  Radicals.  —  In  many  chemical  reactions  the 
elementary  atoms  change  places,  not  with  other  elementary 
atoms,  but  with  groups  of  atoms,  which  appear  to  sustain  rela- 
tions to  the  compounds  they  leave  or  enter  similar  to  those  of 
the  elements  themselves.  Thus,  if  we  add  to  a  solution  of  ar- 
gentic nitrate  a  solution  of  ammonic  chloride,  we  get  the  reac- 
tion expressed  by  the  equation 

AgNO,  +  NH{  01  =  NH.-NO,  +  Ag  CL  [20] 

Here  the  group  NH±  has  taken  the  place  of  Ag.  So,  also, 
in  the  reaction  of  hydrochloric  acid  on  common  alcohol,  the 
group  02#5  in  the  molecule  of  alcohol  changes  places  with  the 
atom  of  hydrogen  in  the  molecule  of  hydrochloric  acid,  — 

C2ff5-0-H+  HCl  =  H-0-H+  C2ff5-CL          [21] 

Alcohol.  Ethylic  Chloride. 

We  write  the  symbols  in  this  peculiar  way  in  order  to  make 
it  evident  to  the  eye  that  such  a  substitution  has  taken  place. 
Lastly,  in  the  reaction  of  chloroform  on  ammonia,  the  group 
Cffof  the  first  changes  places  with  the  three  atoms  of  hydro- 
gen of  ammonia  gas,  — 


OH--  C13  +  H,N  =  ZHCl  +  GffiN.  [22] 

Chloroform.  Hydrocyanic  Acid. 

Such  groups  as  these  are  called  compound  radicals.  Like 
the  atoms  themselves,  they  cannot,  as  a  rule,  exist  in  a  free 
state  ;  but  aggregates  of  these  radicals  may  exist,  which  sus- 
tain the  same  relation  to  the  radicals  that  elementary  substances 
hold  to  the  atoms.  Thus,  as  we  have  a  gas  chlorine  consisting 
of  molecules,  represented  by  Cl-  Cl,  so  there  is  a  gas  cyanogen 
consisting  of  molecules,  represented  by  CN-CN  ,  where  CWis 
a  compound  radical  called  cyanogen.  Again,  the  important 
radicals  CO,  S02,  and  PC13,  are  also  the  molecules  of  well- 
known  gases.  These  radical  substances  correspond  to  the  ele- 
mentary substances  previously  mentioned,  in  which  the  mole- 
cule is  a  single  atom. 

But  with  few  exceptions  the  radical  substances  have  never 


CHEMICAL  NOTATION.  39 

been  isolated,  and  the  radicals  are  only  known  as  groups  of 
atoms  which  pass  and  repass  in  a  number  of  chemical  reac- 
tions. Indeed,  in  the  same  compound  we  may  frequently 
assume  several  radicals.  The  possible  radicals  of  a  chemi- 
cal symbol  correspond  in  fact  almost  precisely  to  the  possi- 
ble factors  of  an  algebraic  formula,  and  in  writing  the  sym- 
bol we  take  out  the  one  or  the  other,  as  the  chemical  change 
we  are  studying  requires.  A  number  of  these  radicals  have 
received  names,  and  among  those  recognized  in  mineral  com- 
pounds a  few  of  the  most  important  are 

Hydroxyl  HO  Sulphuryl  S0t 

Hydrosulpkuryl  HS  Carbonyl  CO 

Ammonium  II^N  Phosphoryl  PO 

Amidogen  H2N  Nitrosyl  NO 

Cyanogen  CN  Nitryl  N0a. 

The  radicals   recognized  in   organic   compounds   are  very 
numerous,  and  will  be  tabulated  hereafter. 


Questions   and   Problems. 

1.  For  what  do  the  following  symbols  stand  ? 

jRT;      Ca,; 


2.  For  what  do  the  following  symbols  stand  ? 

07;     S3-,     0-0-,    H,N;    ff.SO^    3C.2ffG0. 


3.  For  what  do  the  following  symbols  stand  ? 

0;     H,-,     Se-Se-,     NaCl;     H.O  ;     3KN03. 

4.  Analyze  the  following  reaction.     Show  that  the  same  number 
of  atoms  are  represented  on  each  side  of  the  equation,  and  state  the 
class  to  which  it  belongs. 

Fe  +  (ZffCl  +  A(f)  =  (Fed,  +  Aq)  +  HI-HI. 

Hydrochloric  Acid  Ferrous  Chloride. 

5.  Analyze  the  following  reaction.     Show  in  what  the  equality 
consists,  and  state  the  class  to  which  the  reaction  belongs. 


Ammonic  Nitrate.       Water.       Nitrous  Oxide. 


6.  Analyze  the  following  reaction.      Show  in  what  the  equality 
consists,  and  state  the  class  to  which  the  reaction  belongs. 

r+  o--o  —   co». 

Carbon.      Oxyten.     Carbonic  Ar.hydr'.lc. 


40  CHEMICAL  NOTATION. 

7.  Analyze  the  following  reaction.     Show  in  what  the  equality 
consists,  and  state  the  class  to  which  the  reaction  belongs. 

2ff-0-ff+  Na-Na  =  2Na-0-H  +  H-H. 

Water.  Sodium.  Sodic  Hydrate. 

8.  The  following  reaction  may  be  so  written  as  to  indicate  that 
the  products  are  formed  by  a  metathesis  between  two  similar  mole- 
cules.    It  is  required  to  show  that  this  is  possible. 


+     N-JT. 

Ammonia  gas.  Hydrogen  gas.          Nitrogen  gas. 

9.  Write  the  reactions  [17]  and  [18]  so  as  to  indicate  the  manner 
in  which  the  metathesis  is  supposed  to  take  place. 

10.  State  the  conditions  which  determine  the  metathesis  in  the 
various  reactions  given  in  this  chapter  so  far  as  these  conditions  are 
indicated. 

11.  Write  the  reactions  [21]  and  [22]  so  as  to  indicate  the  mariner 
in  which  the  metathesis  is  supposed  to  take  place. 

12.  Analyze  the  following  reaction.     Show  what  determines  the 
metathesis  and  also  what  is  meant  by  a  compound  radical. 


(Pb=(N03)2 

Plumbic  Nitrate.  Ammonic  Chloride. 


Pb€l2  +  (2Nff4-N03  +  Aq) 

Plumbic  Chloride.  Ammonic  Nitrate. 

13.  Compare  with  [22]  the  following  reaction  and  point  out  the 
two  radicals,  which,  as  we  may  assume,  hydrocyanic  acid  contains. 

(Ag-NO,  +  H-CN+  Aq)  =  Ag-CIV  +  (H-NOS  +  Aq) 

Argentic  Nitrate.  Hydrocyanic  Acid.  Argentic  Cyanide.  Nitric  Acid. 

14.  When  sulphuric  anhydride  (S03)  is  added  to  water  (H.2O)  a 
violent  action  ensues  and  sulphuric  acid  is  formed.     The  reaction 
may  be  written  in  two  ways,  and  it  is  required  to  explain  the  different 
views  of  the  process,  which  the  following  equations  express. 

ff20+  SOs  =  ff2SO, 
or  2H-0-H  +  S0,=  0  =  Iff  Of  SO,  +  Hf  0. 

15.  State  the  distinction  between  a  chemical  element  and  an 
elementary  substance.     Give  also  the  distinction  between  a  com- 
pound radical  and  a  radical  substance. 

16.  Give  the  names  of  the  following  radicals. 

HO-,  HS;  NH±;  NH^  S02;   CO-,  PO-,  N02. 


CHAPTER    VI. 

STOCHIOMETRY. 

23.  Stochiometry.  —  The  chemical  symbols  enable  us  not 
only  to  represent  chemical  changes,  but  also  to  calculate  ex- 
actly the  amounts  of  the  substances  required  in  any  given  pro- 
cess as  well  as  the  amounts  of  the  products  which  it  will  yield. 
Each  symbol  stands  for  a  definite  weight  of  the  element  it  rep- 
resents, that  is,  for  the  weight  of  an  atom  ;  but,  as  only  the  rela- 
tive values  of  these  weights  are  known,  they  are  best  expressed 
as  so  many  parts.  Thus  H  stands  for  1  part  by  weight  of 
hydrogen,  the  unit  of  our  system.  In  like  manner  0  stands 
for  16  parts  by  weight  of  oxygen,  N  for  14  parts  by  weight 
of  nitrogen,  G  for  12  parts  by  weight  of  carbon,  C5  for  60  parts 
by  weight  of  carbon,  and  so  on  for  all  the  symbols  in  Table  IL 
The  weight  of  the  molecule  of  any  substance  must  evidently 
be  the  sum  of  the  weights  of  its  atoms,  and  is  easily  found, 
when  the  symbol  is  given,  by  simply  adding  together  the 
weights  which  the  atomic  symbols  represent.  Thus  Jf20 
stands  for  2  +  1 6  =  18  parts  of  water,  H^Nkr  34-14  =  17 
parts  of  ammonia  gas,  and  <72Z^02  f°r  24 -|-  4  -f-  32  =  SO 
parts  of  acetic  acid.1 

Having  then  given  the  symbol  of  a  substance,  it  is  very  easy 
to  calculate  its  percentage  composition.  Thus,  as  in  60  parts  of 
acetic  acid  there  are  24  parts  of  carbon,  in  100  parts  of  the 
acid  there  must  be  40  parts  of  carbon,  and  so  for  each  of  the 
other  elements.  The  result  appears  below ;  and  in  the  same 
way  the  percentage  composition  both  of  alcohol  and  ether  has 
been  calculated  from  the  accompanying  symbol. 

1  In  this  book  "  the  molecular  weight  of  a  substance  "  will  always  mean  the 
sum  of  the  atomic  weights  of  the  atoms  composing  one  molecule,  and  we  shall 
use  the  phrase,  "  the  molecular  weight  of  a  symbol ,"  or  "  the  total  atomic  weight 
of  a  symbol,"  to  denote  the  sum  of  the  atomic  weights  of  all  the  molecules  which 
the  symbol  represents. 


42  STOCHIOMETRY. 

Acetic  Acid  Alcohol  Ether 

CtHtOz.  C2H60.  Ck-HioO. 

Carbon              40.00  52.18  64.86 

Hydrogen           6.67  13.04  13.52 

Oxygen             53.33  34.78  21.62 

100.00  100.00  100.00 

The  rule,  easily  deduced,  is  this :  As  the  weight  of  the  mole- 
cule is  to  the  weight  of  each  element,  so  is  one  hundred  parts  to 
the  percentage  required. 

On  the  other  hand,  having  given  the  percentage  composition, 
it  is  easy  to  calculate  the  number  of  atoms  of  each  element  in 
the  molecule  of  the  substance.  This  problem  is  evidently  the 
reverse  of  the  last,  but  it  does  not,  like  that,  always  admit  of  a 
definite  solution  ;  for,  while  there  is  but  one  percentage  compo- 
sition corresponding  to  a  given  symbol,  there  may  be  an  infinite 
number  of  symbols  corresponding  to  a  given  percentage  com- 
position. For  example,  the  percentage  composition  of  acetic 
acid  corresponds  not  only  to  the  formula  C.2H±0.2,  given  above, 
but  also  to  any  multiple  of  that  formula,  as  can  easily  be  seen 
by  calculating  the  percentage  composition  of  CH20,  C3ff60Sy 
(74/7804,  &c.  They  will  all  necessarily  give  the  same  result, 
and,  before  we  can  determine  the  absolute  number  of  atoms  of 
each  element  present,  we  must  have  given  another  condition, 
namely,  the  sum  of  the  weights  of  the  atoms,  or,  in  other 
words,  the  molecular  weight  of  the  substance.  When  this  is 
known,  the  problem  can  at  once  be  definitely  solved. 

Suppose  we  have  given  the  percentage  composition  of  alco- 
hol, as  above,  and  also  the  further  fact  that  its  molecular  weight 
is  46.  We  can  then  at  once  make  the  proportion 

100  :  52.18  =  46  :  x  =  24  the  weight  of  the  atoms  of  carbon, 
100 : 13.04  =  46  :  x  =    6    "        "       "     "       "      "  hydrogen, 
100 :  34.78  =  46  :z=  16   "       "       "    "      "      "oxygen. 

Then  it  follows  that 

f  |  =  2  the  number  of  atoms  of  carbon  in  one  molecule, 
%  =  6    "          "        u       "       "  hydrogen  in  one  molecule, 
^|  =  1    "         "        "       "       "   oxygen  in  one  molecule. 

It  is  evident  from  this  example,  that,  in  order  to  determine 


STOCHIOMETRY.  43 

exactly  the  symbol  of  a  compound,  we  must  know  its  molecular 
weight.  When  the  substance  is  a  gas,  or  is  capable  of  being 
changed  into  vapor,  we  can  easily  determine  its  molecular 
weight  by  the  principle  on  page  18 .  The  molecular  weight  is 
simply  twice  its  specific  gravity  referred  to  hydrogen.  For  all 
the  problems  given  in  this  book,  which  deal  only  with  the  com- 
mon gases  and  vapors,  the  molecular  weight  can  be  at  once 
taken  from  Table  III.  If  we  are  dealing  with  a  new  substance, 
we  must  determine  its  specific  gravity  experimentally  by  one  of 
the  methods  which  will  hereafter  be  described. 

When,  on  account  of  the  fixed  nature  of  the  substance,  the 
last  mo'de  of  investigation  is  impossible,  we  can  still  frequently 
determine  with  great  probability  the  molecular  weight,  by  study- 
ing the  chemical  reactions  into  which  the  substance  enters,  and 
connecting,  by  careful  quantitative  experiments,  the  molecular 
weight  sought  with  that  of  some  substance  whose  molecular 
weight  is  known.  The  methods  used  in  such  cases  will  be  in- 
dicated hereafter ;  but  even  when  all  such  means  fail,  we  can 
nevertheless  always  find  which  of  all  possible  symbols  ex- 
presses the  composition  of  the  substance  we  are  studying  in 
the  simplest  terms,  in  other  words,  with  the  fewest  number  of 
atoms  in  the  molecule.  Suppose  the  substance  to  be  cane  sugar, 
which  cannot  be  volatilized  without  decomposition,  and  of  which 
no  reaction  is  known  which  gives  any  definite  clew  to  its  mole- 
cular weight.  Peligot's  analysis,  cited  on  page  9,  shows  that  it 
contains,  in  100  parts,  42.06  parts  of  carbon,  6.50  parts  of 
hydrogen,  and  51.44  parts  of  oxygen.  Assume  for  the  mo- 
ment that  the  molecular  weight  is  equal  to  100  then 

=  3.50  the  number  of  atoms  of  carbon. 
JJ2  —  6.50    "         "         «      "       «   hydrogen. 

51:g4  =  3.22    «         «         "      «       «   oxygen. 

This  would  be  the  number  of  atoms  of  each  element  if  the 
sum  of  the  atomic  weight,  that  is,  the  molecular  weight,  of 
sugar,  were  equal  to  100.  As,  from  the  very  definition,  frac- 
tional atoms  cannot  exist,  these  numbers  are  impossible,  but 
any  other  possible  number  of  atoms  must  be  either  a  multiple 
or  a  submultiple  of  the  numbers  found ;  and  we  can  easily  dis- 


44  STOCHIOMETRT. 

cover  the  fewest  number  of  whole  atoms  possible,  by  seeking  for 
the  three  smallest  whole  numbers  which  stand  to  each  other 
in  the  relation  of  3.50  :  6.50  :  3.22,  a  proportion  which  is  very 
nearly  satisfied  by  12  :  22  :  11.  Hence,  the  simplest  possible 
symbol  is  O^H^O^  and  this  has  been  adopted  by  chemists  as 
the  symbol  of  cane  sugar,  although,  from  anything  we  as  yet 
know,  the  symbol  may  be  a  multiple  of  this.  If  now,  taking 
this  symbol  as  our  starting-point,  we  calculate  the  percentage 
composition  which  would  exactly  correspond  to  it,  we  obtain 
the  following  results,  which  we  have  arranged  in  a  tabular 
form,  so  that  the  student  may  compare  the  theoretical  compo- 
sition with  the  numbers  Peligot  obtained  by  actual  analysis. 

Composition  of  Cane  Sugar, 


Peligot's  Analysis.  Theoretical. 

Carbon                      42.06  42.11 

Hydrogen                    6.50  6.43 

Oxygen                     51.44  51.46 

100.00  100.00 

The  difference  between  the  two  is  now  seen  to  be  within  the 
probable  errors  of  analysis,  and  this  example  illustrates  the 
method  of  arranging  analytical  results  generally  adopted  by 
chemists. 

From  the  above  discussion  we  can  easily  deduce  a  simple 
arithmetical  rule  for  finding  the  symbol  of  a  compound  when 
its  percentage  composition  is  known.  But  this  rule  may  be  best 
expressed  in  an  algebraic  formula,  which  will  show  to  the  eye 
at  once  the  relation  of  the  quantities  involved  in  the  calcula- 
tion, and  enable  us  to  extend  our  method  to  the  solution  of 
many  classes  of  problems  which  we  might  not  otherwise  foresee. 
Let  us  then  represent 

By  M  the  weight  of  any  chemical  compound  in  grammes. 
44    m   the   molecular    weight  of  the   compound  in  hydrogen 

atoms. 
"    W  the  weight  of  any  constituent  of  that  compound,  whether 

element  or  compound  radical,  in  grammes. 
"    w   the   total  atomic  weight  of  element  or  radical  in  one 

molecule. 


STOCHIOMETRY.  45 


—  =  proportion  by  weight  of  the  constituent  in  the  compound, 


Then 
w 
m 
and 


^-  =  weight  of  constituent  in  M  grammes  of  compound,  or 

771 

W=M-.  [23] 


Any  three  of  these  quantities  being  given,  the  fourth  can,  of 
course,  be  found.  Thus  we  may  solve  four  classes  of  problems. 

1.  We  may  find  the  weight  of  any  constituent  in  a  given 
weight  of  a  compound,  when  we  know  the  molecular  weight  of 
the  compound  and  the  total  atomic  weight  of  the  constituent  in 
one  molecule. 

Problem.  It  is  required  to  find  the  weight  of  sulphuric 
anhydride  S03  in  4  grammes  of  plumbic  sulphate  PbO,  S03. 
Here,  w  =  32  -f  3  X  16  =  80,  m  =  207  +  16  +  80  =  303, 
and  M=  4.  Ans.  1.056  grammes. 

2.  We   can  find  the  weight  of  a  compound  which  can  be 
produced  from,  or  corresponds  to,  a  given  weight  of  one  of  its 
constituents,  when  the  same  quantities  are  known  as  above. 

Problem.  How  many  grammes  of  crystallized  green  vitriol, 
FeS04.  7ff20,  can  be  made  from  5  grammes  of  iron?  Here, 
w  =  56,  m  =  278,  W=  5.  '  Ans.  24.821. 

3.  We  can  find  the  molecular  weight  of  a  compound  when 
we  have  given  the  weight  of  one  constituent  in  a  given  weight 
of  the  compound,  and  the  total  atomic  weight  of  that  constitu- 
ent in  the  molecule. 

Problem.  In  7.5  grammes  of  ethylic  iodide,  there  are  6.106 
grammes  of  iodine ;  the  total  atomic  weight  of  iodine  in  one 
molecule  is  127.  What  is  the  molecular  weight  of  ethylic 
iodide?  Ans.  156. 

4.  We  can  find  the  total  atomic  weight  of  one  constituent  of 
a  molecule  when  the  molecular  weight  is  given,  and  also  the 
weight  of  the  constituent  in  a  known  weight  of  the  compound. 


46  STOCHIOMETRY. 

Problem.     The  molecular  weight  of  acetic  acid  is  60,  the 
per  cent  of  carbon  in  the  compound  40.     What  is  the  total 
atomic    weight  of    carbon   iii  one    molecule  ?      Ans.  24. 
Whence  number  of  carbon  atoms  in  one  molecule,  2. 

The  last  problem  is  essentially  the  same  as  that  of  finding 
the  symbol  of  a  compound  when  its  percentage  composition  is 
given,  while  the  first  corresponds  to  the  reverse  problem  of 
deducing  the  percentage  composition  from  the  symbol.  By  a 
slight  change  the  formula  can  be  much  better  adapted  to  this 
class  of  cases.  For  this  purpose  we  may  put  M  =  1  00,  since 
we  are  solely  dealing  with  per  cents,  and  also  put  w  =  na, 
a  standing  for  the  atomic  weight  of  any  element,  and  n  for  the 
number  of  atoms  of  that  element  in  one  molecule  of  the 
compound  we  are  studying.  We  then  have 


100  a 


[24] 
L      J 


The  first  of  these  forms  is  adapted  for  calculating  the  per  cent 
of  each  element  of  a  compound  when  the  molecular  weight, 
the  number  of  atoms  of  each  element  in  one  molecule,  and  the 
several  atomic  weights,  are  known  ;  and  it  is  evident  that  all 
these  data  are  given  by  the  chemical  symbol  of  the  compound. 
The  second  of  these  forms  enables  us  to  calculate  the  number 
of  atoms  of  each  element  present  in  one  molecule  of  a  com- 
pound when  the  percentage  composition,  the  molecular  weight, 
and  the  several  atomic  weights,  are  known,  and  illustrates  the 
principle  before  developed,  that  the  molecular  weight  is  an 
essential  element  of  the  problem. 

24.  Stochiometrical  Problems.  —  The  principles  of  the  pre- 
vious section  apply  not  only  to  single  molecular  formulas,  but 
obviously  may  also  be  extended  to  the  equations  which  repre- 
sent chemical  changes.  Since  the  molecular  symbols  which 
are  equated  in  these  expressions  represent  known  relative 
weights,  it  must  be  true  in  every  case  that  we  can  calculate  the 
weight  of  either  of  the  factors  or  products  of  the  chemical 
change  it  represents,  provided  only  that  the  weight  of  some  one 
is  known.  If  we  represent  by  w  and  m  the  total  atomic  weight 
of  any  two  symbols  entering  into  the  chemical  equations,  and 
by  W  and  M  the  weight  in  grammes  of  the  factors  or  products 


STOCHIOMETRY.  47 

which  these  symbols  represent,  then  the  simple  algebraic 
formulae  of  the  last  section  will  apply  to  all  stochiometrical 
problems  of  this  kind,  as  well  as  to  those  before  indicated. 
These  formulae,  however,  are  merely  the  algebraic  expression 
of  the  familiar  rule  of  three,  and  all  stochiometrical  problem  < 
are  solved  more  easily  by  this  simple  arithmetical  rule.  Usin^ 
the  word  symbol  to  express  the  sum  of  the  atomic  weights  it 
represents,  we  may  state  the  rule  as  applied  to  chemical  prob- 
lems in  the  following  words,  which  should  be  committed  to 
memory. 

Express  the  reaction  in  the  form  of  an  equation  ;  make  then 
the  proportion,  As  the  symbol  of  the  substance  given  is  to  the  sym- 
bol of  the  substance  required,  so  is  the  weight  of  the  substance 
given  to  x,  the  weight  of  the  substance  required ;  reduce  the 
symbols  to  numbers,  and  calculate  the  value  of  x. 

This  rule  applies  equally  well  to  all  problems,  like  those  of 
the  last  section,  in  which  the  elements  or  radicals  of  the  same 
molecular  symbol  are  alone  involved  ;  only  in  such  cases  there 
is  of  course  no  equation  to  be  written.  A  few  examples  will 
illustrate  the  application  of  the  rule. 

Problem  1.  We  have  given  10  kilogrammes  of  common  salt, 
and  it  is  required  to  calculate  how  much  hydrochloric  acid  gas 
can  be  obtained  from  it  by  treating  with  sulphuric  acid.  The 
reaction  is  expressed  by  the  equation 

(2Na  01  +  ff2S04  +  Aq)  =  (Na2S04  +  Aq)  +  2IH@/, 
whence  we  deduce  the  following  proportion, 

117  73 

2NaCl.:  2ffCl=  10  :  x  =  Ans.  6.239  kilogrammes. 

Problem  2.  It  is  required  to  calculate  how  much  sulphuric 
acid  and  nitre  must  be  used  to  make  250  grammes  of  the 
strongest  nitric  acid.  The  reaction  is  expressed  by  the 
equation 

KNO,  +  ff,  S04  =  K,  ffS04  +  HNOfr 
whence  we  get  the  proportions 

63  98 

JffN03 :  HzSO±  =  250  :  x  =  Ans.  1.  388.9  grammes  sulphuric 
acid. 

fiS  101.1 

s :  KN03  =  250:x  =  Ans.  2.  401.2  grammes  nitre. 


48 


STOCHIOMETRY. 


The  student  should  also  solve  by  the  same  rule  the  problems 
given  in  the  last  section. 

25.  Gay-Lussac's  Law.  —  This  eminent  French  chemist  was 
the  first  to  state  clearly  the  important  truth,  that,  when  gases  or 
vapors  react  on  each  other,  the  volumes  both  of  the  factors  and 
of  the  products  of  the  reaction  always  bear  to  each  other  some 
very  simple  numerical  ratio.  This  truth  is  generally  known  as 
the  law  of  Gay-Lussac,  but,  since  the  principle  is  a  direct  con- 
sequence of  the  atomic  theory,  it  is  best  studied  in  that  relation. 
It  is,  as  we  have  seen,  a  fundamental  postulate  of  the  theory  that 
equal  volumes  of  all  substances,  when  in  the  aeriform  condition, 
contain  the  same  number  of  molecules.  Hence  it  follows,  that 
the  volumes  of  all  single  molecules  are  the  same,  and,  if  we  take 
this  common  volume  as  our  unit  of  measure,  it  follows,  further, 
that  the  total  molecular  volume  represented  by  any  symbol  is 
always  equal  to  the  number  of  molecules.  We  are  thus  led  to 
a  most  important  fact,  which  gives  an  additional  meaning  to  our 
chemical  symbols,  for  it  appears  that  Every  chemical  equation, 
when  properly  written,  represents  not  only  the  relative  weights, 
but  also  the  relative  volumes  of  its  factors  and  products,  when  in 
the  state  of  gas. 

This  principle  is  illustrated  by  the  following  equations : 


+ 


Carbonic  Anhydride.         Aqueous  Vapor 


Nitric  Oxide  Gas. 


Hydrogen  Gaa. 


Ammonia  Gas. 


Aqueous  Vapor. 


The  squares  which  here  serve  to  indicate  equal  volumes, 
and  to  impress  on  the  mind  the  meaning  of  the  symbols,  are 
evidently  unnecessary  and  will  not  be  used  hereafter. 

The  important  rule  of  the  last  section  may  be  expressed  by 
the  following  proportion 

nm:n'm':=  W:  W'  =  W:W 

Here  m  and  m'  represent  the  molecular  weights  of  any  two 
substances,  n  and  n'  the  number  of  molecules  of  these  sub* 


STOCHIOMETRY.  49 

stances,  which  take  part  in  a  chemical  reaction  whether  as 
factors  or  products,  while  n  m  and  n'  my  represent  what  in  the 
statement  of  our  rule  we  have  called  the  symbols  of  the  sub- 
stances, and  the  equation  expresses  the  fact  that  the  sum  of 
the  atomic  weights  indicated  by  the  symbols  is  proportional 
to  the  weights  of  the  substances  involved  in  the  chemical  reac- 
tion, whether  these  weights  are  estimated  in  grammes  or  in 
criths  (2). 

Now  by  (17)  m'  =  2  Sp.  Gr.  and  by  [3]  W  =  V  X  Sp.  Gr. 

Making  these  substitutions  we  may  reduce  the  above  propor- 
tion to  the  following  form 

£n  m  :  n'  =  W  :  V 

and  this  gives  us  another  stochiometrical  rule,  by  which  we  can 
calculate  the  volume  of  a  gas  or  vapor  involved  in  a  chemical 
reaction,  when  the  weight  of  some  other  factor  or  product  is 
known,  or  inversely,  when  the  volume  is  given  calculate  the 
weight. 

Express  the  reaction  in  an  equation  ;  make  then  the  propor- 
tion, As  one  half  of  the  symbol  of  the  first  substance  is  to  the 
number  of  molecules  of  the  second,  so  is  the  weight  in  criths  of 
the  first  to  the  volume  in  litres  of  the  second  ;  reduce  the  symbol 
to  numbers,  and  calculate  the  value,  of  the  unknown  quantity. 

This  rule  has  the  same  general  application  as  the  first,  and 
a  few  examples  will  illustrate  the  use  of  it. 

Problem  1.  How  much  chlorate  of  potash  must  be  used  to 
obtain  one  litre  of  oxygen  gas  ?  The  reaction  is  expressed  by 
the  equation 


whence  we  get  the  proportion 

122.6 

£(2K  C103)  :  3  =  x  :  1  .     x  =  40.9  criths, 
40.9  X  0.0896  =  Ans.  3.664  grammes. 

Problem  2.  How  many  litres  of  oxygen  gas  can  be  obtained 
from  500  grammes  of  chlorate  of  potash  ?  The  reaction  is  the 
same  as  before,  but  in  this  case  the  grammes  must  first  be 
reduced  to  criths.  The  proportion  will  then  be  written 

4 


50  STOCHIOMETRY. 


KC10:  3  =  :  x  =  Ans.  136.G  litres. 


In  applying  the  rules  of  this  chapter  to  the  solving  of 
stochiometrical  problems,  the  student  should  carefully  bear  in 
mind,  first,  that  the  rule  of  (24)  applies  to  all  those  cases  in 
which  the  weight  of  one  substance  is  to  be  calculated  from  the 
weight  of  another  ;  secondly,  that  when  volume  is  to  be  deduced 
from  volume  the  answer  can  be  found  by  mere  inspection  of 
the  equation  according  to  the  principles  stated  in  (25),  and 
thirdly,  that  the  rule  of  page  49  applies  only  to  those  problems 
in  which  volume  is  to  be  calculated  from  weight,  or  the  reverse. 
In  using  this  last  rule  it  must  be  remembered  that  the  "  first 
substance  "  is  always  the  one  whose  weight  is  given  or  sought, 
while  the  "  second  substance  "  is  always  the  one  whose  volume 
is  given  or  sought. 

Moreover,  the  student  will  notice  that  the  volume  of  any 
aeriform  factor  or  product  may  also  be  found  by  dividing  its 
weight  in  grammes,  —  calculated  by  the  rule  of  (24),  —  by  the 
known  weight  of  one  litre  of  the  gas  or  vapor,  found  from 
Table  III.  by  [3]. 


Questions  and  Problems. 

1.  What  is  the  molecular  weight  of  plumbic  sulphate,  Pb=02=SOz? 
Of  calcic  phosphate,   Ccr3106l(PO)2?     Of  ammonia  alum, 
(NHt\,  [4Ja]|08|(S0a)4.  24#20?  Ans.  303,  310,  and  906.8. 

2.  What  are  the  molecular  weights  of  the  symbols 

3C2ff402-,  5(FeS04.  7ff20)  and  7K2=OfCO? 

Ans.  180,  1390,  and  967.4. 

3.  Are  the  total  atomic  weights  of  the  two  members  of  the  follow- 
ing reaction  equal  ?  * 

Fe  +  (H2S04  +  Ag)  =  (FeSOt  +  Aq)  +  H-H. 
Ans.  The  total  weight  of  each  member  of  the  equation  is  154. 

4.  Calculate   the  percentage  composition  of  ammonic  chloride, 
NH^CL     Ans.  Nitrogen,  26.17;  Hydrogen,  7.48;  Chlorine,  66.35. 

5.  Calculate  the  percentage  composition  of  nitrobenzole,  C^H^NO.^ 
Ans.  Carbon,  58.53;  Hydrogen,  4.07  ;  Nitrogen,  11.39  ;  Oxygen, 

26.01. 


STOCHIOMETRY.  51 

6.  Given  the  percentage  composition  of  chloroform  as  follows  : 
Carbon,  10.04;  Hydrogen,  0.83;  Chlorine,  89.13.  Required  the 
symbol,  knowing  that  the  Sp.  Gr.  of  chloroform  vapor  equals  59.75. 

Ans. 


7.  Given  the  percentage  composition  of  stanno-diethylic  bromide 
as  follows:  Tin,  35.13;  Carbon,  14.29;  Hydrogen,  2.97;  Bromine, 
47.61.     Required  the  symbols,  knowing  that  the   Sp.  Gr.  of  the 
vapor  equals  168.  Ans.  Sn  C4HloBr2. 

8.  Given  the  percentage  composition  of  ethylene  chloride  as  fol- 
lows :  Carbon,  24.24  ;  Hydrogen,  4.04  ;  Chlorine,  71.72.     Required 
the  symbol,  knowing  that  the  Sp.  *Gr.  of  the  vapor  equals  49.5. 

Ans. 


9.  Given  the  percentage  composition  of  cream  of  tartar  as  fol- 
lows: Potassium,  20.79;  Hydrogen,  2.66;  Carbon,  25.52;  Oxygen, 
51.03.     Required  the  simplest  symbol  possible.        Ans.  KH^CtOy 

10.  Given  the  percentage  composition  of  crystallized  ferrous  sul- 
phate as   follows:    Iron,   20.15;    Sulphur,  11.51;    Oxygen,   23.02; 
Water,  45.32.     Required  the  simplest  symbol  possible. 

Ans.  Estimating  the  number  of  molecules  of  water  (T^O),  as 
if  water  were  a  fourth  element  with  an  atomic  weight  of  18,  we  get 
FeSO,.  7H20. 

11.  The  percentage  composition  of  morphia  according  to  Liebig's 
analysis  is  Carbon,  71.35  ;  Hydrogen,  6.69  ;  Nitrogen,  4.99  ;  Oxy- 
gen (by  loss),  16.97.     What  is  the  symbol  of  this  alkaloid,  and  how 
closely  does  this  symbol  agree  with  the  results  of  analysis  ? 

Ans.  The  symbol  C17/719AT03  wouM  require  71.58  Carbon,  6.66 
Hydrogen,  4.91  Nitrogen,  and  16.85  Oxygen. 

12.  It  is  required  to  find  the  weight  of  phosphorus  in  155  kilos. 
of  calcic  phosphate  (Ca3P2^8)'  Ans<  31  kilos. 

13.  It  is  required  to  find  the  weight  of  sulphuric  anhydride  (S03} 
in  284  kilos,  of  sodic  sulphate,  Na2S04.  Ans.  160  kilos. 

14.  How  many  grammes  of  plumbic  sulphate,  (PbSO^  can  be 
made  from  2.667  grammes  of  sulphuric  anhydride  (503) 

Ans.  10.1  grammes. 

15.  How   many  grammes  crystallized  cupric  sulphate   (Cw504. 
67720)  will  yield  317  grammes  of  copper  ?      Ans.  1337  grammes. 

16.  Required   the   total  molecular  weight  of  crystallized   sodic 
phosphate,  knowing  that  71.6  parts  of  the  salt  contain  9.2  parts  of 
sodium,  and  that  the  total  atomic  weight  of  sodium  in  one  mole- 
cule of  the  compound  is  46.  Ans.  358. 


52  STOCHIOMETRY. 

17.  The  molecular  weight  of  potassic  nitrate  is  101.1,  and  2.359 
grammes  of  the  salt  contain  1.120  grammes  of  oxygen.     What  is 
the  total  atomic  weight  of  oxygen,  and  also  the  number  of  oxygen 
atoms  in  one  molecule  ? 

Ans.  Total  atomic  weight  48.     No.  of  oxygen  atoms  3. 

18.  How  much  nitric  acid  (HNO^  is  required  to  dissolve  3.804 
grammes  of  copper  (CV)  and  how  much  cupric  nitrate  (CuN^O^ 
and  how  much  nitric  oxide  (NO)   will  be  formed  in  the  process  V 
The  reaction  is  expressed  by  the  equation 


Ans.  10.08  grammes  of  nitric  acid;  11.244  grammes  of  cupric 
nitrate  and  1.20  grammes  of  nitric  oxide. 

19.  How  much  common  salt  (NaCl)  must  be  added  to  a  solution 
containing  30  grammes  of  argentic  nitrate  (AgNOs)  in  order  to 
throw  down  the  whole  of  the  silver,  and  how  much  argentic  chloride 
(AgCF)  will  be  thus  precipitated  ? 


(AgNO,  +  NaCl  +  Aq)  =  AgCI  +  (NaNO,  +  Aq). 
Ans.  10.32  grammes  of  salt  and  25.32  grammes  argentic  chloride. 


20.  How  many  litres  of  ammonia  gas  (SSTllj)  and  how  many  of 
chlorine  gas  (^1-^oJl  are  required  to  make  one  litre  of  nitrogen  gas 
S^SS"  ?  How  many  litres  of  hydrochloric  acid  gas  (HK2J1)  are 
also  formed  ? 

2S3HI3  +  3(oJl-(oJl  =  6H3(£J1  -|-  S9XS31. 

Ans.  2  litres  of  ammonia  gas  ;  3  litres  of  chlorine  gas,  and  6 
litres  of  hydrochloric  acid  gas. 


21.  How  many  litres  of  hydrochloric  acid  gas  (IHOl)  and  how 
many  of  oxygen  gas  (©=©)  can  be  obtained  from  one  litre  of 
aqueous  vapor  (IILzdD),  and  how  many  litres  of  chlorine  gas 
must  be  used  in  the  process  ? 

4- 


Ans.  2  litres  of  hydrochloric  acid  gas,  £  litre  of  oxygen  gas,  and 
1  litre  of  chlorine  gas.    . 

22.  How  many  litres  of  oxygen  gas  ((o>(£))  are  required  to  burn 
completely  (i.  e.  to  combine  with)  one  litre  of  alcohol  vapor 
((Bailie©),  and  how  many  litres  of  carbonic  anhydride  (OCDa)  and 
how  many  of  aqueous  vapor  (m2(o))  are  formed  by  the  process  ? 
The  chemical  reaction  which  takes  place  when  alcohol  burns  is 
expressed  by  the  equation 


STOCHIOMETRY.  53 

3®=©  = 


Ans.   3  litres  of  oxygen  gas  ;  2  litres  of  carbonic  anhydride,  and 
3  litres  of  aqueous  vapor. 

23.  How  many  litres  of  oxygen  gas  are  required  to  burn  one 
litre  of  arseniuretted  hydrogen  (IH3l^s)>  and  how  many  litres  of 
arsenious  acid  vapor  (ys\s©3)  and  how  many  of  aqueous  vapor  are 
formed  in  the  process  V 

4IH3As  -f  9  ©<c)  —  4^s©3  +  6HI2(o). 

Ans.  2|-  litres  of  oxygen  gas  ;  1  litre  arsenious  acid  vapor  and  1^ 
litres  of  aqueous  vapor. 

24.  How  many  litres  of  chlorine  gas  can  be  made  with  19.49 
grammes  of  manganic  oxide  (MnO-2)  ? 

]?InO,+  (4Jfa+Ag)  =  (Mn  Cl2+2ff20+Aq)  +O1-OL 

Ans.  5  litres. 

25.  How  many  grammes  of  chalk  (CaC03)  are  required  to  yield 
one  litre  of  carbonic  anhydride  ? 


CaCO3  +  (2Ha  +  Aq)  =  ( 

Ans.  4.48  grammes. 

26.  How  many  litres  of  hydrochloric  acid  gas  (HCl)  can  be  made 
with  8.177  kilogrammes  of  common  salt  (NaCl)  ? 

(2Na  Cl  +  ff2S04  +  Aq)  =  (Na.2SO±  +  Aq)  +  2  SSOl. 

Ans.  3120. 

27.  How  many  grammes  of  ferrous  sulphide  (FeS)  are  required 
to  yield  568  cTln.3  of  sulphuretted  hydrogen  (H2S)  ? 

FeS  +  (R2SO,  +  Aq)  =  (FeS04  +  Aq)  +  SlaS. 

Ans.  2.24  grammes. 


CHAPTER    VII. 

CHEMICAL    EQUIVALENCY. 

26.  Chemical  Equivalents.  —  If  in  a  solution  of  argentic 
sulphate  we  place  a  strip  of  metallic  copper,  we  find  after  a 
short  time  that  all  the  silver  has  separated  from  the  solution, 
and  that  a  certain  quantity  of  copper  has  dissolved  in  its  place. 


(AffaS04  +  Aq)  +  CU  =  (  CuSOt  +  Aq)  +  Ag2.     [25] 

If  now  we  pour  off  the  solution  of  cupric  sulphate,  and  place 
in  this  solution  a  strip  of  metallic  zinc,  the  metallic  copper  in 
its  turn  will  all  separate,  and  to  replace  it  a  certain  amount  of 
zinc  will  dissolve. 


(CuS04  +  Aq)  +  Zn  =  (ZnS04  +  Aq)  +  Cu.        [26] 

Lastly,  if  we  pour  off  the  solution  of  zincic  sulphate,  and 
place  in  this  a  strip  of  metallic  magnesium,  the  zinc  will  in  like 
manner  be  replaced  by  magnesium. 

(ZnSOt  +  Aq)  +  Xl§  =  (MgSO,  +  Aq)  +  Zn.       [27] 

In  experiments  like  these,  we  can  by  proper  analytical 
methods  determine  the  relative  quantities  by  weight  of  the 
several  metals  which  thus  replace  each  other,  and  we  find  that 
they  are  always  the  same.  Thus,  if  our  first  solution  contained 
108  milligrammes  of  silver,  the  amount  of  each  metal  suc- 
cessively dissolved  and  precipitate'd  would  be,  of  copper, 
31.7  m.  g.,  of  zinc,  32.6  m.  g.,  of  magnesium,  12  m.  g.  More- 
over, if,  instead  of  using  in  our  experiments  a  metallic  sulphate, 
we  take  a  metallic  chloride,  nitrate,  acetate,  or  any  other  com- 
pound of  the  metals,  we  find  that  the  same  definite  ratios  are 
preserved,  at  least  in  every  case  where  the  substitution  is  pos- 
sible. It  would  appear  then  that  these  relative  quantities  of 
the  several  metals  exactly  replace  each  other  in  all  such  cases. 
They  are,  therefore,  regarded  as  the  chemical  equivalents  of 


CHEMICAL  EQUIVALENCY.  55 

each  other,  in  the  sense  that  they  are  capable  of  filling  each 
other's  place. 

In  a  strict  sense,  two  quantities  of  different  elements  can 
be  said  to  be  equivalent  to  each  other  only  when  they  are 
actually  capable  of  replacing  each  other  in  some  known  chem- 
ical reaction,  but  formerly  the  word  was  used  with  a  much 
wider  significance,  and  quantities  of  two  different  elements 
were  said  to  be  equivalent  to  each  other  if  they  had  been 
proved  to  be  equivalent  to  the  same  quantity  of  some  third 
element  which  served  as  a  link  of  connection.  In  this  way 
an  equivalency  may  be  established  between  all  the  chemical 
elements,  and  the  system  of  chemistry  still  used  in  many  text- 
books is  based  on  a  system  of  equivalency  so  determined.  If 
the  table  of  chemical  equivalents  on  this  old  system  is  com- 
pared with  a  table  of  atomic  weights  on  the  new,  it  will  be 
found  that  the  numbers  of  the  one  are  either  the  same  as  those 
of  the  other,  or  else  some  very  simple  multiples  of  them.  The 
one  set  of  numbers  can  be  used  in  all  stochiometrical  calcula- 
tions in  the  same  way  as  the  other,  and  on  the  old  system  the 
symbols  stand  for  equivalents,  as  in  the  new  they  stand  for 
atomic  weights.  The  equivalents  have  this  advantage,  that 
they  are  the  result  of  direct  experiments,  and  are  based  on  no 
hypothesis  in  regard  to  the  molecular  constitution  of  matter. 
But  this  hypothesis  is  necessary,  in  order  to  correlate  a  large 
number  of  facts  which  modern  chemicil  investigation  has 
brought  to  light,  and  when  once  made,  the  rest  of  the  system 
follows  as  a  necessary  consequence. 

27.  Quantivalence  and  Atomicity  of  the  Elements.  —  If  now, 
starting  with  the  atomic  weights  as  they  have  been  determined 
or  assumed  in  Table  II.,  we  compare  together  the  different 
elements  from  the  point  of  view  taken  in  the  last  section,  it 
will  be  found,  that,  while  in  some  cases  one  atom  of  one  ele- 
ment is  the  equivalent  of  one  atom  of  another,  in  other  cases, 
it  may  be  the  equivalent  of  two,  three,  or  four  atoms.  Since 
in  the  system  of  this  book  the  symbols  always  stand  for  atomic 
weights,  the  relation  here  referred  to  is  made  evident  whenever 
any  metathetical  reaction  is  expressed  in  the  form  of  an  equa- 
tion. A  few  examples  will  illustrate  the  point,  and  make 
clear  what  is  meant.  The  reaction  of  aqueous  hydrochloric 
acid  on  a  solution  of  argentic  nitrate  is  expressed  by  the 
equation, 


56  CHEMICAL  EQUIVALENCY. 

(AgNO,  +  HGl  +  Aq)  =  (HN08  +  Aq)  +  AgCl,    [28] 

and  here  evidently  Ag  changes  places  with  H,  and  hence  one 
atom  of  silver  is  equivalent  to  one  atom  of  hydrogen.  Take 
now  the  reaction  of  dilute  sulphuric  acid  on  zinc,  which  is 
expressed  by  the  equation, 

Zn  +  (ffaS04  +  Aq)  =  (ZnS04  +  Aq)  +  HMH,    [29] 

and  it  will  be  seen  that  Zn  has  changed  places  with  H^  and 
hence  that  one  atom  of  zinc  is  the  equivalent  of  two  atoms  of 
hydrogen.  Lastly,  in  the  reaction  of  water  on  phosphorous 
trichloride,  expressed  by  the  equation, 

in 

/r  o  Tf/yj    I      i 

l3  =  oJiCyl-j-2 

iphorous  Acid. 


=  3HCI  -f  ffsP03,  [30] 

Phosphorous  Acid. 


it  is  equally  evident  that  P  has  changed  places  with  H&  and 
hence  in  this  reaction  one  atom  of  phosphorus  is  equiva- 
lent to  three  atoms  of  hydrogen. 

This  relation  of  the  elements  to  each  other  is  called  by 
Hofmann  quantivalence  ;  arid  selecting  here,  as  in  the  system  of 
atomic  weights,  the  hydrogen  atom  as  our  standard  of  reference, 
the  atoms  of  different  elements  are  called  wmvalent,  bivalent, 
Invalent,  or  quadrivalent,  according  as  they  are  in  the  sense 
already  indicated  equivalent  to  one,  two,  three,  or  four  atoms 
of  hydrogen.  These  terms  are  very  appropriate,  since  they 
are  all  derived  from  the  same  root  as  our  common  English 
word  equivalent,  which  best  expresses  the  fundamental  idea 
that  underlies  the  whole  subject.  We  shall  therefore  adopt 
them  in  this  book,  and,  as  Hofmann  recommends,  designate 
the  quantivalence,  whenever  important,  by  a  Roman  numeral 
placed  over  the  atomic  symbol  thus, 

i          ii       m       iv 
<?/,       0,      N,       G. 

In  most  cases,  however,  the  quantivalence  is  indicated  with 
sufficient  clearness  by  the  dashes,  which  are  also  used  in  this 
book  to  separate  the  parts  of  a  molecular  symbol.  The  num- 
ber of  these  dashes  is  always  the  same  as  the  quantivalence 
of  the  atoms,  or  groups  of  atoms,  on  either  side. 


CHEMICAL   EQUIVALENCY.  57 

With  these  additions  to  our  notation  we  are  able  to  express 
by  our  symbols  all  that  was  valuable  in  the  old  system  of 
equivalents,  and  at  the  same  time  all  that  is  peculiar  to  our 
modern  theories. 

Precisely  the  same  relations  of  quantivalence  are  manifested 
even  more  fully  by  the  compound  radicals,  whenever  in  a 
chemical  reaction  they  change  places  with  elementary  atoms, 
and  their  replacing  value  is  indicated  in  the  same  way.  Thus, 
in  the  following  reaction, 

C2ff30-Cl+ff-0-ff—ff-Cl+II-0-C2H30,       [31] 

Acetyl  chloride.  Water.  Acetic  Acid. 

the  radical  C2ff3  0,  named  acetyl,  changes  places  with  one  atom 
of  hydrogen,  and  is  therefore  univalent,  while  in  the  next, 

m  I  in 

Cff=-  C13  +  ff3N  =  3HOI  +  CH=-N,  [32] 

Chloroform.  Hydrocyanic  Acid. 

the  radical  CH\s  as  evidently  trivalent. 

The  quantivalence  of  an  element  or  radical  is  shown,  not  only 
by  its  power  of  replacing  hydrogen  atoms,  but  also  by  its  power 
of  replacing  any  other  atoms  whose  quantivalence  is  known. 
Moreover,  what  is  still  more  important,  the  quantivalence  of  an 
element  or  radical  is  shown,  not  only  by  its  replacing  power,  but 
also  by  what  we  may  term  its  atom-fixing  power,  that  is,  by  its 
power  of  holding  together  other  elements  or  radicals  in  a  mole- 
cule. We  may  take  as  examples  the  molecules  of  four  very 
characteristic  compounds,  namely,  hydrochloric  acid,  water, 
ammonia,  and  marsh  gas,  whose  symbols  may  be  written  thus, 

i  IT  in  iv 

H-Cl        ft  H-0   ft  ft  H=-N      ft  ft  ft  H^G. 

Hydrochloric  Acid.          Water.  Ammonia.  Marsh  Gas. 

By  these  symbols  it  appears,  that,  while  the  univalent  atom  of 
chlorine  can  hold  but  one  atom  of  hydrogen,  the  bivalent  atom 
of  oxygen  holds  two,  the  trivalent  atom  of  nitrogen  three,  and 
the  quadrivalent  atom  of  carbon  four  atoms  of  the  same  ele- 
ment. It  appears,  then,  that  the  Roman  numerals  or  dashes, 
which  represent  the  replacing  power  of  the  atoms  or  radicals, 
represent  also  the  atom-fixing  power  of  the  same,  measured 
in  each  case  by  the  number  of  atoms  of  hydrogen,  or  their 


58  CHEMICAL  EQUIVALENCY. 

equivalents,  with  which  these  atoms  or  radicals  can  combine 
to  form  a  single  molecule.  On  account  of  the  importance  of 
this  principle  we  will  extend  our  illustrations  to  a  number  of 
other  compounds,  and  the  student  should  carefully  compare 
in  each  case  the  quantivalence  on  the  two  sides  of  the  dash 
or  dashes,  which  mark  the  atom-fixing  power  of  the  dominant 
atom  in  the  molecule. 

ii  ii  ii  ii 

Na-Cl  K-I          C,H,-Br          K-CN; 

Sodic  Chloride.      Potassic  Iodide.      Ethylic  Bromide.       Potassic  Cyanide. 

i    ii    i  ii     n          i     ii      i  i   n      i 

K-O-H         Pb=0       H-O-NO^       H-0-02ff30', 

Potassic  Hydrate.     Plumbic  Oxide.        Nitric  Acid.  Acetic  Acid. 

i     i      i       in  i          in        i         i  i     in 

ff.  H,  C,  H?N     (  a  H^P      CH3,  C2H*  G,H^N. 

Ethylamine.  Triethyl  phosphine.       Methyl-ethj'1-amyl-amine. 


quantivalence  of  the  chemical  elements,  especially  as 
indicated  by  their  atom-fixing  po\vcr,  is  by  no  means  always 
the  same.  They  constantly  exhibit  under  different  conditions 
an  unequal  atom-fixing  power.  Thus  we  have 

II  IV  III  V  III  V 

Sn  O12  and  Sn  Cl*        PC13  and  PCl&        NH&  and 


Each  element,  however,  has  a  maximum  power,  which  it  never 
exceeds.  This  we  shall  call  its  atomicity,  and  we  shall  distin- 
guish the  elements  as  monads,  dyads,  triad<,  &c.,  according  to 
the  number  of  univalent  atoms  or  radicals  they  are  able  at 
most  to  bind  together.  Thus  nitrogen  is  a  pentad,  although 
it  is  more  commonly  trivalent,  and  lead  is  a  tetrad,  although 
it  is  usually  bivalent.  Again,  sulphur  is  a  hexad,  although 
in  most  of  its  relations  it  is,  like  lead,  bivalent.  In  like 
manner  with  other  elements,  one  of  the  few  possible  con- 
ditions is  generally  much  more  common  and  stable  than  the 
rest,  and  this  prevailing  quantivalence  of  an  element  is  a 
more  characteristic  property  than  its  maximum  quantiva- 
lence or  atomicity.  A  classification  of  the  elements  based  on 
their  atomicity  alone  would  contravene  their  most  striking 
analogies,  while  one  based  on  the  prevailing  quantivalence 
very  nearly  satisfies  all  natural  affinities.  Moreover,  it  should 
be  added,  that,  while  the  prevailing  quantivalence  of  the  ele- 
ments is  generally  well  established,  their  atomicity  is  frequently 


CHEMICAL  EQUIVALENCY.  59 

still  in  doubt ;  for  the  first  can  generally  be  discovered  by  study- 
ing the  simple  compounds  of  the  elements  with  chlorine  or  hy- 
drogen, while  the  last  is  often  only  manifested  in  those  more 
complex  combinations,  in  regard  to  which  a  difference  of  opin- 
ion is  possible. 

The  possible  degrees  of  quantivalence  of  an  elementary 
atom  are  related  to  each  other  by  a  very  simple  law.  They 
are  either  all  even  or  all  odd.  Thus  the  atom  of  sulphur  may 
be  sextivalent,  quadrivalent  and  bivalent,  but  is  never  triva- 
lent  or  univalent ;  and  on  the  other  hand  the  atom  of  nitrogen 
may  be  quinquivalent,  trivalent  and  univalent,  but  not  quad- 
rivalent or  bivalent.  Atoms  like  those  of  sulphur,  whose  quan- 
tivalence is  always  even,  are  called  artiads,  while  those  like 
nitrogen,  whose  quantivalence  is  always  odd,  are  called 


A  change  in  the  quantivalence  of  an  atom  implies  a  change 
in  all  its  chemical  relations,  and  the  differences  between  the 
reactions  of  the  same  atom  in  its  several  states  of  quantivalence 
are  frequently  as  great  as  those  between  the  atoms  of  different 
elements.  Indeed,  the  first  distinction  appears  to  be  only  less 
fundamental  than  the  last,  to  which  chemists  have  attached  so 
great  and  perhaps  undue  importance.  The  ferrous  and  ferric 
compounds  of  iron,  for  example,  would  be  referred  to  different 
elements,  were  it  not  for  the  single  circumstance  that  they  may 
be  derived  from  the  same  substance  and  are  so  readily  converti- 
ble into  each  other.  The  classes  of  compounds  to  which  they 
are  most  closely  related  belong  indeed  to  wholly  different  ele- 
ments ;  for  the  ferrous  compounds  resemble  those  of  zinc,  and 
the  ferric  compounds  those  of  aluminum.  A  multitude  of  simi- 
lar facts  will  be  brought  to  notice  in  Part  II.  of  this  work. 

28.  Atomicity  or  Quantivalence  of  Radicals.  —  When  in  the 
molecule  of  any  compound  the  dominant  or  central  atom  is 
united  to  as  many  other  atoms  as  it  can  hold  of  that  kind,  the 
molecule  is  said  to  be  saturated  ;  thus 

HCl,        H,0,        HsN<        ff4G 

are  all  saturated  molecules  ;  for,  although  nitrogen  is  a  pentad, 
it  cannot  without  the  intervention  of  some  other  atom  or  radical 
hold  more  than  three  atoms  of  hydrogen.  While  on  the  other 
liaad  (he  molecules 

IT  n  IT 

CO, 


60  CHEMICAL  EQUIVALENCY. 

are  not  saturated,  for  they  can  combine  directly  with  more 
oxygen  or  chlorine,  forming  thus  the  saturated  molecules 


If  now  from  a  saturated  molecule  we  withdraw  one  or  more 
atoms  of  hydrogen,  or  their  equivalents,  the  residue  may  be  re- 
garded as  a  compound  radical  with  an  atomicity  equal  to  the 
number  of  hydrogen  atoms,  or  their  equivalents,  withdrawn. 
Thus,  if  from  the  saturated  molecule  of  marsh  gas  H±  0  we 
withdraw  one  atom  of  hydrogen,  we  get  the  radical  methyl 
/7,  O,  which  is  a  monad  ;  if  we  withdraw  two  atoms,  we  have 
the  radical,  H2C,  which  is  a  dyad;  if  we  withdraw  three, 
there  results  HC,  which  is  a  triad  ;  and  lastly,  if  we  with- 
draw all  four,  we  fall  back  on  the  tetrad  atom  of  carbon.  Again, 
if  from  the  saturated  molecule  of  nitric  anhydride  N206  we 
withdraw  one  atom  of  the  dyad  oxygen  0,  it  falls  into  two 
atoms  of  N0.2  each  of  which  is  a  monad.  If  now  we  with- 
draw from  N0.2  one  of  its  remaining  atoms  of  oxygen,  we 
have  left  NO,  which  is  a  triad.  Lastly,  a  molecule  of  sulphuric 
anhydride  S03,  which  is  saturated,  gives,  by  withdrawing  one 
atom  of  oxygen,  SO.^  which  acts  as  a  bivalent  radical.  These 
considerations  lead  us  to  a  simple  rule,  first  stated  by  Wurtz, 
which  in  almost  every  case  will  enable  us  to  infer  the  atomicity 
of  any  given  radical.  The  atomicity  1  of  a  compound  radical 
is  always  equal  to  the  number  of  hydrogen  atoms,  or  their  equiva- 
lents, which  the  radical  may  be  regarded  as  having  lost. 

It  must  not  be  supposed,  however,  that  all  such  radicals  are 
possible  compounds.  In  a  few  cases  only  these  residues,  of 
which  we  have  been  speaking,  form  non-saturated  molecules, 
which  are  capable  of  existing  in  a  free  state,  like  those  of  car- 
bonic oxide,  nitric  oxide  and  sulphurous  acid.  At  other  times 
they  are  compound  radicals,  which,  by  doubling,  form  molecules 
that  can  exist  in  a  free  state,  as  those  of  cyanogen  gas,  and 
perhaps  also  of  some  hydrocarbons.  Again,  they  appear  as 
compound  radicals,  which  pass  and  repass  in  so  many  chemical 
reactions  as  to  almost  force  upon  us  the  belief  that  they  have 
a  real  existence,  and  represent  the  actual  grouping  of  the 
atoms  in  the  compounds  of  which  they  seem  to  be  an  in- 
tegral part.  Still  again,  and  even  more  frequently,  they  can 
only  be  regarded  as  convenient  factors  in  a  chemical  equation. 

1  The  quantivalence  of  a  compound  radical  is  always  the  same  as  its 
atomicity. 


CHEMICAL    EQUIVALENCY.  61 


Questions  and  Problems. 

1.  Analyze  the  following  metathetical  reactions,  showing  in  each 
case  how  many  parts  of  the  several  elements  are  equivalent  to  one 
part  by  weight  of  hydrogen,  and  also  to  how  many  atoms  of  hydro- 
gen one  atom  of  each  of  the  interchanging  elements  corresponds. 
For  the  atomic  weights  refer  to  Table  II. 


2H-0-C2H5  +  K-K=  2K-0-C2H5  +  H-H. 

Alcohol.  "  Potassium.        Potassic  Ethylate. 

2H-0-H+  Mg  =  Mg--0.rHz  +  H-H. 

Water.  JVIagnesic  Hydrate. 


Sb  =  0fff8  +  3HCZ  = 

Antimonious  Hydrate.  Antimonious  Chloride. 

4H-0-H  +  S£C14  =  H/O/Si 

Silicic  Chloride.          Silicic  Acid. 

2  Make  out  a  table  of  chemical  equivalents  so  far  as  the  reactions 
of  this  chapter  will  enable  you  to  deduce  them  from  the  atomic 
weights  given  in  Table  II. 

3.  Analyze  the  following  metathetical  reactions,  showing  in  each 
case  how  the  quantivalence  of  the  several  compound  radicals  in- 
volved in  the  metathesis,  is  indicated. 

H-  0-H+  (  O2ff,  0)-  0-(  C2H6)=(  G2ff3  0}-  0-H-\-H-  0- 

Water.  Acetic  Ether.  Acetic  Acid.  Alcohol. 


-f 

Potassic  Cyanide.          Ethylene  Bromide.  Ethylene  Cyanide.  Potassic  Bromide. 


3H-0-H  +  (C.H^Cl,  =  (03ff^O/H3  +  Sffd. 

Water.  Glyceryl  Chloride.  Glycerine.  Hydrochloric  Acid. 

The  names  of  the  radicals  are  as  follows  :  C27730,  Acetyl  ;  C2H5, 
Ethyl  ;  C2#"4,  Ethylene  ;  C3ff5,  Glyceryl  ;  CN,  Cyanogen. 

4.  What  is  the  atom-fixing  power  or  quantivalence  of  the  differ- 
ent atoms  and  radicals  in  the  following  symbols  ? 


.2=CO  (NH^-O-NO 

Potassic  Sulphantimoniate.     A-id  Sodic  Carbonate.  Ammonic  Ni'rite. 


Oxamide.  Succinamic  Acid.  Tartar  Emetic  (dried)  . 

5.  If  HtO;  C2H6;  CZH,0  (alcohol);  COCl,  (phosgene  gas); 
C2HtO<>  (acetic  acid)  and  C2H204  (oxalic  acid)  arc  saturated  mole- 
cules, what  is  the  atomicity  of  the  radicals  HO  (hydroxyl)  ;  C2/76 
(ethyl)  ;  C3#4  (ethylene)  ;  C,H,0  (aldehyde)  ;  CO  (carbonyl)  ; 
C2//3<9  (acetyl)  and  C2<92  (oxilyl). 


CHAPTER     VIII. 

CHEMICAL    TYPES. 

29.  Types  of  Chemical  Compounds.  —  There  are  three 
modes  or  forms  of  atomic  grouping,  to  which  so  large  a  num- 
ber of  substances  may  be  referred,  that  they  are  regarded  as 
molecular  types,  or  patterns,  according  to  which  the  atoms  of 
a  molecule  are  grouped  together.  These  types  may  be  repre- 
sented by  the  general  formulae  :  — 

IT  iin  i    ii    i 

R  -R  R,R--R    or    R-R-R  [33] 

i    i     i   in  i    i   in    i 

R,  R,  R-R        or         R,  R--R-R. 

It  will  be  noticed,  that  in  the  first  of  these  types  a  single  uni- 
valent  atom  or  radical 1  is  united  to  another  single  univalent 
atom,  that  in  the  second  a  bivalent  atom  binds  together  two 
univalent  atoms  or  their  equivalents,  and  that  in  the  third  a 
trivalent  atom  binds  together  three  univalent  atoms,  or  their 
equivalents.  The  dashes  are  used  to  separate  what  has  been 
called  the  central,  the  dominant,  or  the  typical  atom  from  those 
which  it  thus  unites  into  one  molecular  whole,  and  serve  at 
the  same  time  to  point  out  the  parts  of  the  symbol  to  which 
its  affinities  are  directed.  Commas  are  used  to  separate  the 
subordinate  atoms  so  united.  It  will  be  further  noticed,  that 
in  each  case  the  quantivalence  of  the  dominant  atom  is  equal 
to  the  sum  of  the  quantivalences  of  the  subordinate  atoms,  or 
radicals,  on  either  side;  and  the  peculiarity  in  each  case  consists 
solely  in  the  relations  of  the  parts  of  the  molecule  which  we 
thus  attempt  to  indicate  by  the  symbol.  The  three  compounds, 
hydrochloric  acid,  water,  and  ammonia, 

ii          ii    ii          iiini 
H-  Cl,     H,  H--  0,      H,  H,  H=-N, 

1  Here,  as  elsewhere  through  the  book,  we  use  the  symbol  R  for  any 

univalent,  R  for  any  bivalent,  and  R  for  any  trivalent  atom  or  radical.  More- 
over, to  avoid  unnecessary  repetition,  we  shall  for  the  future  conform  to  the 
general  usage,  and  speak  of  the  atoms  of  a  radical  as  well  as  of  those  of  an 
element,  and  use  the  word  "  atom  "  as  applying  to  both,  although  the  usage 
frequently  involves  an  obvious  solecism. 


CHEMICAL   TYPES.  63 

are  generally  taken  as  representatives  of  these  types,  and  sub- 
stances are  described  as  belonging  to  the  type  of  hydrochlo- 
ric acid,  to  the  type  of  water,  or  to  the  type  of  ammonia,  as 
the  case  may  be.  These  substances,  however,  are  regarded  as 
types  in  no  other  sense  than  that  their  molecules  present  the 
same  mode  of  grouping  which  is  indicated  above  by  the  more 
general  symbols.  Substances  belonging  to  the  same  type  may 
have  widely  different  properties.  To  the  type  of  water  be- 
long the  strongest  alkalies  and  the  most  corrosive  acids  known. 
In  what,  then,  it  may  be  asked,  does  the  type  outwardly  con- 
sist, or  in  what  is  it  manifested  ?  for  the  grouping  of  the  atoms 
can  only  be  a  matter  of  inference.  The  answer  is,  that  the 
type  of  the  molecules  of  a  substance  is  manifested  solely  by 
its  chemical  reactions.  Substances  belonging  to  the  same  type 
are  simply  those  whose  reactions  may  be  classed  together  ac- 
cording to  some  one  general  plan.  Thus  water,  alcohol,  and 
acetic  acid  are  classed  in  the  same  type,  because,  when  submit- 
ted to  the  action  of  the  same  or  similar  reagents,  they  undergo 
a  like  transformation,  which  seems  to  point  to  a  similarity  of 
atomic  grouping. 

#  H-0  -f  PCI,  =  PCl.O  +  H-Cl  +  H-Cl 

Water.  Phosphoric  Chloride.  Hydrochloric  Acid. 

H,  O.2H5=0  +  PCI.  =  PC130  +  H-Cl  +  C.2H6-Cl    [34] 

Alcohol.  Phosphoric  Oxy-chloride.  Ethylic  Chloride. 

H,  C,H.O-0  +  PCI,  =  PC130  +  H-Cl  +  C^O-Cl. 

Acetic  Acid.  Acetylic  Chloride. 

On  studying  these  reactions,  it  will  be  seen  that  both  the  man- 
ner in  which  the  three  compounds  break  up,  and  the  probable 
constitution  of  the  products  formed,  point  to  the  conclusion,  that, 
in  each,  one  bivalent  atom  holds  together  two  univalent  atoms 
or  radicals.  It  will  be  found,  in  the  first  place,  that  in  all  three 
cases  the  reaction  consists  primarily  in  the  substitution  of  two 
atoms  of  chlorine  for  one  of  oxygen  in  the  original  molecule. 
It  will  appear,  in  the  next  place,  that  as  soon  as  this  dominant 
atom,  which  holds  together  the  parts  of  the  molecule,  is  taken 
away,  each  of  the  three  molecules  splits  up  into  two  others  of  a 
similar  type ;  and  lastly,  it  is  evident  from  the  third  example 
that  one  of  the  oxygen  atoms  of  acetic  acid  stands  in  a  very 
different  relation  to  the  molecule  from  the  other.  All  this 


64  CHEMICAL  TYPES. 

points  to  the  inference  just  made.  At  least,  these  and  a  vast 
number  of  similar  reactions  are  best  explained  on  this  hypoth- 
esis, and  herein  its  only  value  lies  and  its  probability  rests. 
In  section  27  we  have  already  given  the  symbols  of  a  number 
of  chemical  compounds  so  printed  that  they  can  be  at  once  re- 
ferred to  one  or  the  other  of  the  three  types  here  alluded  to, 
and  it  will  not,  therefore,  be  necessary  to  multiply  examples  in 
this  place. 

30.  Condensed  Types.  —  In  the  same  way  that  a  bivalent 
atom  may  bind  together  two  univaleut  atoms  or  their  equiva- 
lents, so,  also,  it  may  serve  to  bind-  together  two  molecules,  and, 
in  like  manner,  a  trivalent  atom  may  bind  together  three  mole- 
cules into  a  more  complex  molecular  group  ;  and  thus  are 

formed  what  are  called  condensed  types.     We  may  represent 

i     n    i 
a  double  molecule  of  the  type  of  water  thus,  RfR^R^  but 

it  must  be  borne  in  mind  that  such  a  symbol  stands  for  two 
molecules,  since,  by  the  very  definition,  two  molecules  of  the 
same  kind  cannot  chemically  combine.  We  can,  however, 

solder  them,  as  it  were,  into  one  molecular  whole  by  substituting 

i  n 

for   the   two   univalent   atoms  R.2  a  single  bivalent  atom  R, 

when  we  obtain  a  mode  of  molecular  grouping  represented  by 

i     n    n 

T)    _  T>    _  7~>  r*o  en 

R2-R.2=R,  [35] 

which  may  be  called  the  type  of  water  doubly  condensed.  The 
constitution  of  common  sulphuric  acid  is  best  represented  after 
this  type  by  the  symbol,  — 

n 
R2=02=S02.  [36] 


n 


The  soldering  atom  is  here  the  bivalent  radical  S02.  In  like 
manner,  by  using  a  trivalent  atom,  we  can  solder  together 
three  molecules  of  the  same  water-type,  as  in  the  general 
symbol,  — 

i    n  in 


which  represents  the  type  of  water  trebly  condensed.     In  the 
same  way  we  may  derive  the  symbol,  — 


i    i  in 


CHEMICAL  .TYPES.  65 

which  represents  the  type  of  ammonia  doubly  condensed.  The 
substance  urea,  one  of  the  most  important  of  the  animal  secre- 
tions, is  best  represented  by  a  symbol  after  this  last  type,  — 

H»  ff^N^CO  [39] 

where  the  soldering  atom  is  the  bivalent  radical  carbonyl. 

Chemists  have  also  been  led  to  admit  the  existence  of  what 
are  called  mixed  types,  which  are  formed  by  the  union  of  mole- 
cules of  different  types  soldered  together  by  a  single  multiva- 
lent  atom  or  radical  as  before.  Thus,  the  molecules  of  sul- 
phurous acid  may  be  regarded  as  formed  of  a  molecule  of  water 
soldered  to  a  molecule  of  hydrogen  by  an  atom  of  sulphury  1, 

S02-,  thus,  H-O-Haud  H-H,  united  by  S02  give 


So,  also,  the  composition  of  a  complex  organic  compound 
called  sulphamide,  or  sulphamic  acid,  is  most  simply  expressed 
when  regarded  as  formed  by  the  union  of  water  and  ammonia 
soldered  together  by  the  same  radical  sulphuryl  ;  thus,  from 

in  n  m    n      n 

H,  H-N-H,  and  H-O-HvfQ  have  H,  H=N-S0.2-0-H.       [41] 

Lastly,  if  we  bind  together  on  the  same  principle  molecules 
of  the  type  of  hydrochloric  acid,  we  shall  simply  reproduce 
the  types  of  water  and  of  ammonia,  thus  showing  that  all  the 
types  are  only  condensed  forms  of  the  simplest.  We  must  not, 
therefore,  attach  to  the  idea  of  a  chemical  type  any  deeper  sig- 
nificance than  that  indicated  above.  It  is  simply  a  conven- 
ient ^mode  of  classifying  certain  groups  of  chemical  reactions, 
and  a  help  in  representing  them  to  the  mind;  and  we  may 
regard  the  same  substance  as  formed  on  one  type  or  on  the 
other,  as  will  best  help  us  to  explain  the  reactions  we  are  study- 
ing. Moreover,  it  is  frequently  convenient  to  assume  other  types 
besides  those  here  specially  mentioned. 

31.  Substitution.  —  When  cotton-  wool    is   dipped  in  strong 

nitric  acid   (rendered  still  more  active  by  being  mixed  with 

twice  its   volume  of  concentrated  sulphuric  acid),  and  after- 

wards washed  and  dried,  it  is  rendered  highly  explosive,  and, 

5 


66  CHEMICAL   TYPES. 

although  no  important  change  has  taken  place  in  its  outward 
aspect,  it  is  found  on  analysis  to  have  lost  a  certain  amount  of 
hydrogen  and  to  have  gained  from  the  nitric  acid  an  equivalent 
amount  of  nitric  peroxide  NOZ  in  its  place. 


becomes 

Cotton.  Gun-Cotton. 

Under  the  same  conditions  glycerine  undergoes  a  like  change, 
and  is  converted  into  the  explosive  nitro-glycerine,  — 


becomes 

Glycerine.  Nitro-glycerine. 

So,  also,  the  hydrocarbon  naphtha,  called  benzole,  is  changed 
into  mtro-benzole,  — 

C&  HQ      becomes      C6(H5^02). 

Benzole.  Nitro-benzole. 

The  last  compound  is  not  explosive,  and  the  explosive  nature 
of  the  first  two  is  in  a  measure  an  accidental  quality,  and  is 
evidently  owing  to  the  fact  that  into  an  already  complex  struc- 
ture there  have  been  introduced,  in  place  of  the  indivisible  atoms 
of  hydrogen,  the  atoms  of  a  highly  unstable  radical  rich  in  oxy- 
gen. The  point  of  chief  interest  for  our  chemical  theory  is  that 
this  substitution  does  not  alter,  at  least  essentially,  the  outward 
aspect  of  the  original  compound.  Every  one  knows  how  closely 
gun-cotton  resembles  cotton-wool.  In  like  manner  nitro-glycer- 
ine  is  an  oily  liquid  like  glycerine,  and  nitro-benzole,  although 
darker  in  color,  is  a  highly  aromatic  volatile  fluid  like  benzole 
itself.  Products  like  these  are  called  substitution  products,  and 
they  certainly  suggest  the  idea  that  each  chemical  compound 
has  a  certain  definite  structure,  which  may  be  preserved  even 
when  the  materials  of  which  it  is  built  are  in  part  at  least 
changed.  If  in  the  place  of  firm  iron  girders  we  insert  weak 
wooden  beams,  a  building,  while  retaining  all  its  outward  as- 
pects, may  be  rendered  wholly  insecure,  and  so  the  explosive 
nature  of  the  products  we  have  been  considering  is  not  at  all 
incompatible  with  a  close  resemblance,  in  outward  aspects  and 
internal  structure,  to  the  compounds  from  which  they  were 
derived. 

The  idea  that  each  body  has  a  definite  atomic  structure  is 


CHEMICAL  TYPES.  67 

even  more  forcibly  suggested  by  another  class  of  substitution 
products  first  studied  by  Dumas,  in  which  atoms  of  chlorine, 
bromine,  or  iodine  have  taken  the  place  of  the  hydrogen  atoms 
of  the  original  compound.  Thus,  if  we  act  upon  acetic  acid 
with  chlorine  gas,  we  may  obtain  three  successive  products,  as 
shown  in  the  following  table,  although  only  the  first  and  the 
last  have  been  fully  investigated. 

Acetic  acid  C2F4Oa  or    (CzH36)-^-H 

Chloracetic  acid  C2(H3CI)0Z     "     (CZHZCIO)-0-H 

Dichloracetic  acid         Ct(HtClJO,    «     (C2HC120)-0 -H 

Trichloracetic  acid        C2(HC13)03    «     (C,C7,0)-0-// 

We  cannot,  however,  replace  the  fourth  atom  of  hydrogen 
by  chlorine  ;  and  this  fact  seems  to  prove  that  there  is  a  real 
difference  between  this  atom  of  hydrogen  and  the  other  three, 
and  gives  an  additional  ground  for  the  distinction  we  make 
when  we  write  the  symbol  of  acetic  acid  after  the  type  of  water, 
as  in  the  second  column.  The  three  atoms  of  hydrogen  in  the 
radical  placed  on  the  left-hand  side  of  the  dominant  atom  may 
all  be  replaced  by  chlorine,  but  the  single  atom  of  hydrogen 
placed  on  the  right  cannot.  These  products  all  resemble 
acetic  acid  in  that  they  form  with  the  alkalies  crystalline 
salts,  when  the  fourth  atom  of  hydrogen  is  replaced  by  an 
atom  of  sodium  or  potassium,  as  the  case  may  be. 

It  was  the  study  of  these  and  similar  substitution  products 
which  first  led  to  the  conception  of  chemical  types,  and  the 
word  as  first  used  was  intended  to  convey  the  idea  of  a  definite 
structure,  although  perhaps  as  yet  unknown  ;  but  as  the  theory 
was  extended  more  and  more,  and  to  widely  different  chemical 
compounds,  it  was  found  that  the  first  definite  conception  could 
not  be  maintained,  and  the  idea  gradually  assumed  the  shape  we 
have  given  it  in  the  last  section.  Still,  the  facts  from  which 
the  original  conception  was  drawn  remain,  and  they  point  no 
less  clearly  now  than  they  did  before  to  the  existence  of  a  def- 
inite structure  in  all  chemical  compounds  as  the  legitimate  ob- 
ject of  chemical  investigation. 


68  CHEMICAL  TYPES. 

32.  Isomorphism.  —  Closely  associated  with  the  facts  of  the 
last  section,  which  find  their  chief  manifestation  in  substances 
of  organic  origin,  are  the  phenomena  of  isomorphism,  which 
are  equally  conspicuous  among  artificial  salts  and  native  rain- 
Fig.  i.  erals.     There  seems  to  be  an  intimate 

connection  between  chemical  composition 
and  crystalline  form,  and  two  substances 
which  under  a  like  form  have  an  anal- 
.ogous  composition  are  said  to  be  isomor- 
phous.  Thus  the  following  minerals  all 
crystallize  in  rhombohedrons  (Fig.  1,) 
which  have  very  nearly  the  same  inter- 
facial  angles,  and,  as  the  symbols  show, 
they  have  an  analogous  composition.  They  are  therefore 
isomorphous. 

n    n     n 
Calcite  or  calcic  carbonate 


ii  ii  ii 
Magnesite  or  magnesic  carbonate  Mg=Oz=CO 

n  n  n 
Chalybdite  or  ferrous  Fe=  Oa=  C  0 

n  n  n 
Diallogite  or  manganous  "  Mn-O^CO 

n  ii  n 
Smithsonite  or  zincic  Zn=Oz=CO 

The  most  cursory  examination  of  these  symbols  will  show 
that  they  differ  from  each  other  only  in  the  fact  that  one  me- 
tallic atom  has  been  replaced  by  another.  It  is  not,  however, 
every  metallic  atom  which  can  thus  be  put  in  without  altering 
the  form.  This  is  a  peculiarity  that  is  confined  to  certain 
groups  of  elements,  which  for  this  reason  are  called  groups  of 
isomorphous  elements.  Moreover,  as  a  rule,  there  is  a  close  re- 
semblance between  the  members  of  any  one  of  these  groups  in 
all  their  other  chemical  relations.  These  facts,  like  those  of  the 
last  section,  tend  to  show  that  the  molecules  of  every  substance 
have  a  determinate  structure,  which  admits  of  a  limited  substi- 
tution of  parts  without  undergoing  essential  change,  but  which 
is  either  destroyed  or  takes  a  new  shape  when  in  place  of  one 
of  its  constituents  we  force  in  an  unconformable  element.  A 
well-known  class  of  artificial  salts,  called  the  alums,  affords  even 
a  more  striking  illustration  of  the  principles  of  isomorphism 
than  the  simpler  example  we  have  chosen  ;  but  all  the  bearings 


CHEMICAL   TYPES.  69 

of  the  subject  cannot  be  understood  without  a  knowledge  of 
crystallography,  and  we  must  therefore  refer  for  further  details 
to  works  on  mineralogy. 

33.  Rational  Symbols.  —  Chemical  formulae,  like  those  of 
the  last  few  sections,  which  endeavor,  by  grouping  together  the 
elementary  symbols,  to  illustrate  certain  classes  of  reactions, 
and  to  illustrate  the  manner  in  which  a  complex  molecule  may 
break  up,  are  called  rational  symbols,  and  are  to  be  distinguished 
from  the  simpler  symbols  used  earlier  in  the  book,  which  ex- 
press only  the  relative  proportions  in  which  the  elements  are 
combined,  and  which,  since  they  are  simply  expressions  of  the 
results  of  analysis  on  a  concerted  plan,  are  called  empirical 
symbols.  Whether  these  rational  symbols  can  be  regarded  in 
any  sense  as  indicating  the  actual  grouping  of  the  material 
atoms  is  very  doubtful,  although  facts  like  those  stated  above 
would  seem  to  indicate  that  such  may  be  the  case,  at  least  to  a 
limited  extent.  It  is  difficult,  for  example,  to  resist  the  con- 
clusion that  in  alcohol  and  its  congeners  the  atoms  C2ffs  are 
grouped  together  in  some  sense  apart  from  the  rest  of  the 
molecule ;  but  then  we  have  no  evidence  of  this  grouping  apart 
from  the  reactions  of  these  compounds,  and,  until  greater  cer- 
tainty is  reached,  it  is  not  best  to  attach  a  significance  to  our 
symbols  beyond  the  truths  they  are  known  to  illustrate. 

It  is  objected  to  the  use  of  rational  symbols  that  they  bias 
the'  judgment  on  the  side  of  some  theory,  of  which  they  are 
more  or  less  the  exponents.  But  when  they  are  used  in  the 
sense  stated  above,  this  objection  has  no  force,  for  the  reactions 
they  prefigure  are  no  less  facts  than  the  definite  proportions  they 
conventionally  represent,  and  we  employ  one  mode  of  grouping 
the  symbols  or  another,  as  will  best  indicate  the  reactions  we 
are  studying.  Moreover,  as  science  advances,  we  have  every 
reason  to  believe  that  we  shall  gain  more  and  more  knowledge 
of  the  actual  relations  between  the  parts  of  a  material  molecule, 
and  as  has  already  been  intimated,  there  can  hardly  be  a 
doubt  that  in  some  cases  our  rational  symbols  do  express  even 
now  actual  knowledge  of  this  sort,  however  crude  and  partial 
it  may  be.  Our  present  typical  symbols  are  indeed  the  ex- 
pressions of  partial  generalizations,  which,  however  imperfect, 
have  an  element  of  truth.  Hence  it  is  that  they  have  pointed 
out  new  lines  of  investigation,  have  led  to  new  discoveries,  and 


70  CHEMICAL    TYPES. 

have  been  of  the  greatest  value  to  science.  They  will  doubt- 
less soon  be  superseded  by  other  rational  symbols,  expressing 
other  partial  generalizations,  to  serve  the  same  purpose  in  their 
turn  and  be  likewise  forgotten.  We  must  not,  however,  de- 
spise these  temporary  expedients  of  science.  They  are  not  only 
useful,  but  necessary,  and  cannot  mislead  the  student  if  he  re- 
members that  all  such  aids  are  merely  the  scaffoldings  around 
the  science,  on  which  the  builders  work.  It  is  from  this  point 
of  view  alone  that  we  are  to  look  at  the  whole  idea  of  chemi- 
cal atoms,  which  lies  at  the  basis  of  our  modern  chemical 
philosophy.  That  this  idea  is  actually  realized  in  the  concrete 
form  which  it  takes  in  some  minds,  can  hardly  be  believed. 
The  true  chemical  idea  of  the  atom  is  more  nearly  represented 
by  the  corresponding  Latin  word  individuum.  The  atom  is 
the  chemical  individual,  the  unit,  in  which  the  mind  seeks  to 
repose  for  the  time  the  individuality  of  that  as  yet  undivided 
substance  we  call  an  element. 

34.  Graphic  Symbols.  —  A  more  graphic  method  of  repre- 
senting the  relations  between  the  atoms  of  a  molecule  than 
that  of  our  ordinary  rational  symbols  has  been  contrived  by 
Kekule,  and  has  a  similar  value  in  aiding  the  conceptions,  and 
thus  facilitating  the  study  of  chemistry.  In  describing  this 
system  we  shall  speak  of  the  possibilities  of  combination  of 
any  polyad  atom  with  monad  atoms  as  so  many  centres  of  at- 
traction or  points  of  attachment,  and,  also,  as  so  many  affinities. 
Kekule  represents  a  monad  atom,  with  its  single  centre,  thus,  Q, 
while  the  symbols  (T"7),  (.  .  .),  (.  .  .  .},  &c.,  represent 
polyad  atoms  of  different  atomicities.  When  the  several  affini- 
ties are  satisfied,  the  points  are  exchanged  for  lines  pointing 

in  the  direction  of  the  attached  atoms.     Thus,  the  symbol 

represents  a  dyad  atom  with  its  two  affinities  satisfied  by  two 

ii 
monad  atoms,  as,  for  example,  in  a  molecule  of  water  H-Q-H. 

In  like  manner  the  symbol      (|^({"T)(^TT>T"o    repre- 

v    ii 
sents  a  molecule  of  nitric  anhydride  NtO»  and  the   symbol 

0  !!  ii  0  a  mo^ecu^e  °f  sulphuric  anhydride  S03.  Mole- 
cules like  these,  in  which  all  the  affinities  are  satisfied,  are  said  to 


CHEMICAL   TYPES.  71 

v 

be  saturated  or  closed,  while  the  atomic  group  NO.^  represented 

by  > — ^  — ^N  has  one  point  of  attraction  still  open,  and, 
therefore,  acts  as  a  inonad  radical.  So,  also,  the  molecular 
group  S0.2  represented  by  >  |^-|  p  _  >.,  acts  as  a  dyad  radi- 
cal. 

These  graphic  symbols  enable  us  to  illustrate  several  impor- 
tant principles  which  could  not  readily  be  understood  without 
their  aid. 

First.  In  the  examples  given  in  this  section  thus  far,  the 
quanti valence  of  a  group  of  atoms  of  the  same  element  is 
equal  to  the  sum  of  the  quanti  valences  of  all  the  atoms  of  the 

V    II 

group.  Thus,  in  the  molecule  N205,  the  group  of  two  pentad 
atoms  presents  ten  affinities,  and  is  saturated  by  the  group  of 
five  dyad  atoms,  which  presents  the  same  number  of  affinities 
in  return.  So,  also,  in  the  molecule  SO&  a  group  of  three 
dyad  atoms  just  saturates  the  single  hexad  atom  S.  Such,  how- 
ever, is  not  necessarily  the  case,  for  it  frequently  happens  that 
the  similar  atoms  of  such  groups  are  united  among  them- 
selves, and  that  a  portion  of  the  affinities  (necessarily  always 
an  even  number)  are  thus  satisfied.  For  example,  although 
C  is  a  tetrad  atom,  the  hydrocarbons,  (72/^,  C2ff4,  and  C2ff^  are 
all  saturated  molecules,  as  is  shown  by  the  following  graphic 
symbols, 


and  it  is  evident  that  in  the  first  the  two  carbon  atoms  have 
been  united  by  two,  in  the  second  by  four,  and  in  the  third  by 
six,  of  their  eight  affinities,  while  a  corresponding  number  of 
points  to  which  hydrogen  atoms  might  otherwise  have  been  at- 
tached are  thus  closed. 

In  like  manner  we  have  a  well-known  series  of  hydrocar- 
bons, whose  symbols  are 

CH±,  c^iifo  csiTSi  C^H^  CsHift  CQJETU,  &c., 

the  molecule  of  each  one  differing  from  that  of  the  last  by  the 
group  CH.2.  In  all  these  compounds  the  carbon  atoms  are 


72 


CHEMICAL  TYPES. 


united  among  themselves  at  the  smallest  possible  number  of 
points,  as  is  shown,  in  a  single  case,  by  the  following  graphic 
symbol, 


and  by  constructing  the  graphic  symbols  of  the  other  members 
of  the  series,  it  will  be  easily  seen  that  the  number  of  affinities 
thus  closed  is  in  every  case  equal  to  2  n  —  2,  while  the  number 
remaining  open  is  4  n  —  (2  n  —  2)  =  2  n  -\-  2,  where  n 
stands  for  the  number  of  carbon  atoms  in  the  molecule.  Hence, 
while  the  groups  just  mentioned  form  saturated  molecules,  the 
atomic  groups 


Off, 

Methyl.  Ethyl.  Propyl. 

act  as  univalent  radicals. 

Ci   i   i   0®® 


u  &c., 


Butyl.  Amyl. 

The  graphic  symbol  of  ethyl  is 
,  and  in  a  similar  way  the  graphic  symbols  of 

In  like  manner 


the  other  radicals  may  be  easily  constructed, 
may  be  also  constructed  the  graphic  symbols  of  the  following 
important  compound  radicals,  which  form  a  series  parallel  to 
the  first,  and  are  all  evidently  dyads :  — 


Ethylene. 


Propylene.       Butylene. 


05ffw  &c. 

Amylene. 


Here  again  the  graphic  symbols  enable  us  to  explain  a  remark- 
able fact.  These  last  atomic  groups  act  not  only  as  compound 
radicals,  but  also  form  the  molecules  of  definite  hydrocarbons 
(the  first  in  the  series  being  the  well-known  olefiant  gas),  and 
the  difference  in  these  two  conditions  may  be  represented  to 
the  eye,  in  the  case  of  amylene,  for  example,  as  below :  — 


GGJ 


CiXD      (DO)      QXL> 

Radical  CSH10. 


Hydrocarbon  Cr,H10. 

The  molecule  in  the  first  case  is  open,  and  presents  two  points 
of  attraction,  while  in  the  second  case  it  is  closed. 


CHEMICAL    TYPES.  73 

The  members  of  the  two  classes  of  hydrocarbon  radicals 
mentioned  above  are  the  characteristic  constituents  of  an  im- 
portant class  of  compounds  called  alcohols,  and  hence  they  are 
usually  called  alcohol  radicals.  If,  in  these  atomic  groups,  we 
substitute  oxygen  for  a  portion  of  the  hydrogen,  one  atom  of 
oxygen  always  taking  the  place  of  two  atoms  of  hydrogen,  we 
obtain  still  other  series  of  radicals,  which  are  the  characteristic 
constituents  of  several  important  organic  acids,  and  belong  to 
the  class  of  acid  radicals,  which  will  be  defined  in  the  next 
chapter.  Among  the  most  important  of  the  radicals  thus  de- 
rived are  those  of  the  followin  series  :  — 


OHO         C2H30      -CSH50         C4H70        G5NgO 

Formyl.  Acetyl.  Propionyl.  Butyryl.  Valeryl. 

and  the  student  should  construct  the  graphic  symbol  of  each. 

The  compounds  of  carbon  have  been  selected  to  illustrate 
the  apparent  change  of  atomicity  which  frequently  accompa- 
nies the  grouping  together  of  similar  atoms,  because  this  ele- 
ment is  peculiarly  susceptible  of  such  a  mode  of  combination, 
and  in  fact  the  almost  infinite  variety  of  its  compounds  may  be 
traced  to  this  circumstance.  The  same  phenomenon,  however, 
is  presented,  although  to  a  less  marked  degree,  by  other  ele- 
ments. Thus  arises  the  remarkable  fact  that  a  group  of  two 
atoms  of  a  bivalent  element  has  not  unfrequently  only  the  same 
quantivalence  as  a  single  atom.  For  example,  there  are  two 
compounds  of  mercury  and  chlorine  Hg=Glz  represented  graphi- 

cally by  S=y^  an(^  D^Jfe]  =  C%a  represented  by  ^\r^\-    So  also 

we  have  Cu=0  and  [(7w2]=(9.  We  also  frequently  meet  with 
another  illustration  of  the  same  principle  in  an  important  class 
of  tetrad  elements  whose  atoms  readily  pair  together,  forming 
an  atomic  group  which  is  sexivalent.  Thus  are  formed  the 
well-known  compounds 


When  these  same  elements  enter  into  combination  by  single 
atoms,  they  are  almost  invariably  bivalent,  and  thus  we  have, 
in  several  cases,  two  very  distinct  classes  of  compounds,  the 
one  formed  with  the  single  and  the  other  with  the  double  atom 
of  the  element  ;  for  example, 


74  CHEMICAL    TYPES. 


Fe-Cl2  and    FeWlQ        Fe-0  and 


It  will  be  noticed  that  although  in  the  compounds  of  the 
second  class  the  quantivalence  of  the  single  atoms  is  twice  as 
great  as  it  is  in  the  first,  yet  their  atom-fixing  power  is  only 
increased  by  one  half,  and  hence  the  name  of  ses^m'-oxides 
or  sesgw'-chlorides,  &c.,  which  is  frequently  applied  to  them. 

In  order  to  distinguish  the  groups  of  similar  atoms  whose 
affinities  are  all  open,  from  those  groups  where  the  affinities  are 
in  part  closed  by  the  union  of  the  atoms  among  themselves,  we 
may,  as  above,  enclose  the  symbols  of  the  last  in  brackets  ;  and 
this  rule  will  generally  be  followed.  In  most  cases,  however, 
the  relations  of  the  parts  of  the  symbol  are  sufficiently  evident 
without  this  aid. 

Secondly.  The  graphic  symbols  illustrate  another  important 
theoretical  principle,  which,  although  almost  self-evident,  might 
be  overlooked  if  not  dwelt  upon  specially  ;  namely,  that 
on  the  multivalence  of  one  or  more  of  its  atoms  depends  the 
integrity  of  every  complex  molecule.  According  to  our  pres- 
ent theories,  no  molecule  can  exist  as  an  integral  unit  unless  its 
parts  are  all  bound  together  by  such  atomic  clamps.  More- 
over, the  whole  virtue  of  a  compound  radical  consists  in  the 
circumstance  that  it  is  an  incomplete  structure  of  the  same  sort, 
and  its  quantivalence  is  in  every  case  equal  to  the  number  of 
univalent  atoms  (or  their  equivalents)  which  are  required  to 
complete  it,  or  which  it  may  be  regarded  as  having  lost. 
Hence  the  law  of  Wurtz  finds  a  perfect  expression  in  this  sys- 
tem of  graphic  notation. 

Thirdly.  The  graphic  symbols  illustrate  most  forcibly  the 
relations  of  the  parts  of  a  complex  molecule.  Thus,  for  ex- 
ample, the  symbols  of  alcohol  and  acetic  acid  given  below  show 
r}  —  p)  that  in  these  compounds  the  dominant 
atom  of  oxygen  acts  as  a  bond  uniting 
a  complex  radical  to  a  single  monad 
atom.  They  also  show  how  it  is 
possible  that  three  of  the  atoms  of 
hydrogen  in  acetic  acid  may  stand  in 
a  very  different  relation  to  the  mole- 
cule from  the  fourth  (31).  Again 
they  show  that  the  molecule  of  acetic 
acid  differs  from  that  of  alcohol  in  the 


CHEMICAL   TYPES.  75 

fact  that  one  dyad  atom  has  taken  the  place  of  two  monad 
atoms;  and,  lastly,  they  give  form  to  the  idea  of  chemical 
types,  so  far  as  it  has  any  real  significance.  When  the  com- 
position of  a  compound  is  represented  in  this  way,  all  the 
accidental  or  arbitrary  divisions  of  our  ordinary  notation  dis- 
appear, and  only  those  are  preserved  which  are  fundamental. 
We  gain  thus  more  accurate  conceptions  of  molecular  struc- 
ture. We  understand  better  the  relations  of  the  various  com- 
pound radicals  (compare  §  28),  and,  above  all,  we  thus  realize 
the  full  meaning  of  the  fundamental  tenet  of  our  new  philoso- 
phy, which  holds  that  each  chemical  molecule  is  a  completed 
structure  bound  together  in  all  its  parts  by  a  system  of  mutual 
attractions. 

There  is  another  system  of  graphic  symbols,  frequently  used 
in  works  on  modern  chemistry,  which  has  some  advantages 
over  the  one  just  described.  In  this  system  the  atoms  are 
represented  by  small  circles  circumscribing  the  ordinary  sym- 
bol, and  the  atomicity  is  indicated  by  dashes  radiating  from 
these  circles.  A  few  examples  will  sufficiently  illustrate  the 
application  of  this  method. 

®    ®  ®    © 

ll  I        II 

©-©-©        ©-©-©-©-©        ®-©-©-©-® 

Water  II  I 

H-O-H  @     @  @ 

Alcohol.  Acetic  Acid. 

CZH3-0-H.  C2H30.0-H. 

It  is  obvious,  however,  that  the  circles  here  used  are  not  es- 
sential, and  if  we  omit  them,  and  only  use  dashes  between  the 
dominant  atoms,  and  also,  for  convenience  in  printing,  bring  the 
whole  expression  into  a  linear  form,  using  commas  to  separate 
disconnected  atoms,  and  such  other  signs  as  may  be  necessary  to 
avoid  ambiguity,  we  have  at  once  the  ordinary  system  of  nota- 
tion adopted  in  this  book.  The  graphic  symbols  last  described 
are  merely  an  expansion  of  this  system.  Nevertheless,  the  prac- 
tice of  developing  the  ordinary  symbols  into  either  of  the  more 
graphic  forms  will  tend  to  impress  the  full  meaning  of  the 
symbols  on  the  mind  of  the  student,  and  will  thus  greatly  aid 
him  in  acquiring  a  clear  conception  of  the  theory  of  modern 
chemistry. 


76  CHEMICAL   TYPES. 

We  may,  however,  extend  the  use  of  dashes  so  as  to  indicate 
the  relations  of  all  the  parts  of  a  complex  molecule  by  our  or- 
dinary notation.  Thus  we  may  write  the  symbol  of  alcohol 

or  that  of  acetic  acid 


and  these  expanded  symbols  may  frequently  be  used  to  ad- 
vantage in  place  of  the  graphic  forms.  When  thus  developed, 
the  symbol  indicates  the  quantivalence  of  each  of  the  atoms  of 
the  molecule,  and  in  every  case,  if  the  symbol  is  correctly 
written,  the  number  of  dashes  will  be  one  half  of  the  total 
quantivalence  of  all  the  atoms  which  are  thus  grouped  together, 
for  each  dash  evidently  represents  two  affinities. 

The  remarks  at  the  close  of  the  last  section  apply,  of  course, 
still  more  forcibly  to  such  bold  and  material  conceptions  as 
these  graphic  symbols  appear  to  represent,  and  when  we  re- 
call the  hooked  atoms  of  an  elder  philosophy,  we  cannot  but 
smile  to  think  how  closely  our  modern  science  has  reproduced 
what  we  once  considered  as  strange  and  grotesque  fancies.  But, 
absurd  as  such  conceptions  certainly  would  be,  if  we  supposed 
them  realized  in  the  concrete  forms  which  our  diagrams  em- 
body, yet,  when  regarded  as  aids  to  the  attainment  of  general 
truths,  which  in  their  essence  are  still  incomprehensible,  even 
these  crude  and  mechanical  ideals  have  the  very  greatest  value, 
and  cannot  well  be  dispensed  with  in  the  study  of  science. 

Questions  and  Problems. 

1.  To  what  types  may  the  following  symbols  be  referred,  and  what 
is  the  quantivalence  of  the  different  compound  radicals  here  distin- 
guished ?  Study  with  the  same  view  the  symbols  already  given  in 
the  previous  chapter. 


fr(07ff*0) 

izole.  Oil  of  Bitter  Almonds.  Ethylene.  Gly collie  Acid. 


H-0-(C7H.O)     SfC 

Phenic  Acid.  Benzoic  Acid.  Glycol.  Oxalic  Acid. 


Aniline.  Benzamide. 

/  Q    TJ \  \-ftT  TT 

Ethylene  diamine. 


CHEMICAL    TYPES.  77 

ZT,  H-N-(  C2H2 OyO-H  H,  H-N-(  C2 02)- 0-H 

Glycocol.  Oxamic  Acid. 

ff,  ( C7H5  0}=N-(  C2H2 0)-  0-H      H,  H-N-(  C2 0,)- 0-(  G,H6) 

Hippuric  Acid.  Oxamethane. 

2.  Analyze  the  following  reactions,  and  show  that  by  comparing 
the  reactions  in  each  group,  the  typical  structure  of  the  various 
compounds  may  be  inferred. 

d-d        +        H-H       =        HCl        +        HCl 

Chlorine  gas.  Hydrogen  gas.  Hydrochloric  Acid.         Hydrochloric  Acid. 

Cl-Cl  .   +     (C7H50)-H  =    (C7H50)-Cl   +     HCl 

Oil  of  Bitter  Almonds.  Benzoyl  Chloride. 


H-Cl      +      K-O-H  =        KGl      +  H-O-H 

Potassic  Hydrate.  Potassic  Chloride.  Water. 

H-Cl    +     (C.H^-O-H  =     (C.2H5)-Cl    +  H-O-H 

Alcohol.  Ethylic  Chloride. 


H,H=S   +    PWl,    =  PiCkS   +  HCl  +  HCl 

Sulphohydric  Acid.    Phosphoric  Chloride. 


H,  (  C2H3  Oy-S  +  Pi  Glt  =  Pi  Cl»  S  +  (  C*H»  0)-  Cl  +  HCl 

Thiacetic  Acid.  Acetyl  Chloride. 


KfOfHi  +  (CO),  H~=N  =  KfOf(CO}  +  H, 

Potassic  Hydrate.  Cyanic  Acid.  Potessic  Carhonate.  Ammonia. 


N=  K2=0.2=(CO)+H,  H, 

Cyanic  Ether.  Ethylamine. 

3.  What  would  be  the  symbols  of  cyanic  acid  and  cyanic  ether  (see 
last  problem),  on  the  supposition  that  they  contain  the  radical  cyan- 
ogen, and  are  formed  after  the  water  type  ?  Is  the  following  reaction 
compatible  with  that  last  given  ? 


K-0-H+  (C<,H,)-0-(CN)  =  (C2H5)-0-H+  K-( 

Cyanetholine.  Alcohol.  Potassic  Cyanate. 

and  if  not,  what  conclusion  must  you  draw  in  regard  to  the  two 
compounds  cyanic  ether  and  cyanetholine  ? 

4.  What  bearing  have  the  phenomena  of  substitution  on  the  doc- 
trine of  chemical  types  ?     Does  the  circumstance  that  the  proper- 

1  This  product  in  the  actual  process  is  decomposed  by  the  excess  of  potash 
into  potassic  carbonate  and  ammonia. 


78  CHEMICAL    TYPES. 

ties  of  the  substitution  products  are  frequently  quite  different  from 
those  of  the  original  substance  invalidate  the  doctrine  ? 

5.  How  does  the  action  of  chlorine  on  acetic  acid  indicate  that 
this  compound  is  fashioned  after  a  determinate  type  ?     On  what 
particular  fact  does  this  evidence  chiefly  rest  V 

6.  What  bearing  have  the  phenomena  of  isomorphism  on  the  doc- 
trine of  types  ?     Enforce  the  argument  by  some  familiar  illustra- 
tion. 

7.  The  radical  allyl  C3H5  is  univalent  in  oil  of  garlic  (C3#"5)2=S, 
and   in    allylic    alcohol    (C3H5)-0-H,    but    trivalent  in  glycerine 
(C*H^=OfHy    Moreover,  this  radical  when  set  free  doubles,  forming 
a  volatile  hydrocarbon  oil,  which  has  the  composition  (C3PI^(C3H^), 
and  which  combines  directly  with  bromine,  the  resulting  product  hav- 
ing the  symbol  (C3H^-(CzH^Br^.    Represent  these  symbols  by  the 
graphic  method,  and  thus  explain  the  different  relations  of  the 
radical. 

8.  Represent  the  symbols  of  phenic  acid  and  benzoic  acid  by  the 
second  graphic  method,  and  explain  why  the  radical  phenyl  (C6f/5) 
and  benzoyl  (C77J50)  are  only  univalent. 

9.  Why  is  it  that  the  addition  of  the  atoms  CH2  does  not  change 
the  atomicity  of  a  radical  ? 

10.  What  is  the  quantivalence  of  Al  in  the  symbol  \_Al- Al~]iCl6! 
Is  there  any  difference  in  the  quantivalence  of  Fe  in  the  two  com- 
pounds Fe=Oz=CO  and  [Fe-Fe]i0J(S02)8?  Answer  the  questions  by 
the  aid  of  graphic  symbols. 

11.  Is  there  any  difference  in  the  quantivalence  of  nitrogen  in 
potassic  nitrite  K-O-NO  and  potassic  nitrate  K-O-NO^ 

12.  Represent  by  graphic  symbols  the  difference  between  cyanic 
ether  and  cyanetholine  (see  problems  2  and  3  above). 

13.  The  symbol   \Hg^\Clt  represents  a  single  molecule,  while 
NazCl2  represents  two  molecules,  and  would  be  more  properly  writ- 
ten 2NaCl.     What  is  the  difference  in  the  two  cases  ? 

14.  Represent  by  the  graphic  method  the  symbols  of  potassic  car- 
bonate K<f02=(CO)   and  potassic  oxalate  KfO<=(CzO^),  and  show 
that  both  form  a  perfect  molecular  unit. 

15.  Represent  by  the  graphic  method  the  following  symbols  ; 

Hf  Of(  03ff6)         (Propyl  Glycol.)  ; 
H2=0<?(C3HtO)     (Lactic  Acid.)  ; 


CHEMICAL  TYPES.  79 

H.f  0,=(  C,H,  0.2)    (Malonic  Acid)  ; 
Sf  Of(  C3  03)        (Unknown), 

and  thus  show  that  they  are  formed  after  the  same  type. 

16.  What  is  the*  atom-fixing  power  or  quantivalence  of  the  ele- 
ments and  radicals,  which  appear  in  the  various  symbols  given  in 
this  chapter  ?  Develop  these  symbols,  and  show  that  they  repre- 
sent in  each  case  a  single  perfect  molecule. 

N.  B.  The  student  should  practice  developing  the  ordinary  mole- 
cular symbols  into  the  graphic  forms  described  above,  until  he  is  per- 
fectly familiar  with  the  method,  and  has  acquired  a  clear  conception 
of  the  different  types  of  molecular  structure. 


CHAPTER   IX.1 

BASES,    ACIDS,    AND    SALTS. 

35.  Hydrates,  Alkalies,  Bases.  —  It  is  not  unfrequently  the 
case  that  the  technical  terms  of  a  science  remain  in  use  long 
after  they  have  lost  their  original  meaning.  This  is  peculiarly 
true  of  those  which  we  have  placed  at  the  head  of  this  section. 
They  have,  with  the  exception  of  the  first,  come  down  to  us 
from  the  period  of  alchemy,  and  are  still  retained  in  the  lan- 
guage of  trade  and  in  many  works  on  practical  science,  with  a 
peculiar  meaning  which  they  have  acquired  during  the  last 
hundred  years  under  the  teaching  of  the  dualistic  theory. 
Since  they,  in  many  cases  at  least,  suggest  erroneous  concep- 
tions in  regard  to  the  constitution  of  chemical  compounds,  it 
would  be  well  if  they  could  be  discarded  altogether  ;  but,  as 
this  is  impracticable,  we  must  endeavor  to  give  to  them  as 
definite  a  meaning  as  possible. 

The  term  "  hydrate  "  is  applied  to  a  class  of  compounds  which 
were  formerly  supposed  to  contain  water  as  such,  but  which  are 
now  believed  to  have  no  closer  relation  to  water  than  is  indi- 
cated by  the  circumstance  that  they  have  the  same  type,  and 
may  be  formed  from  water  by  replacing  one  of  its  hydrogen 
atoms  with  some  metal.  Thus,  by  acting  on  water  with  potas- 
sium, we  obtain  potassic  hydrate  ;  or,  if  we  use  sodium,  we  ob- 
tain sodic  hydrate. 


2ff-0-H+  K-K=<2K-0-ff-\-  H-H 

Water.  Potassium.       Potassic  Hydrate.    Hydrogen  Gas. 

[42] 
2H-0-H+  Na-Na  =  2  Na-O-H  +  H  H 

Water.  Sodium.  Sodic  Hydrate.        Hydrogen  Gas. 

Both  of  these  hydrates,  and  also  those  of  the  very  rare  but 
closely  allied  metals,  lithium,  caesium,  and  rubidium,  are  very 

1  In  studying  this  chapter  the  student  should  endeavor  to  remember  the 
names  and  symbols  of  the  different  compounds  mentioned.  Hitherto  we 
have  been  chiefly  employed  with  the  forms  of  the  symbols,  and  this  exercise 
of  the  memory  has  not  been  expected. 


BASES,  ACIDS,  AND  SALTS.  81 

in  water,  MIX!  yield  solutions  which  corrode  the  skin,  and 
i,  ih<i  fats  into  soaps.  To  all  the  substances  known  to 
them  which  possessed  these,  caustic,  qualities  the  alchemists 
gave  the  name  of  alkalies,  arid  this  term  is  now  applied  to  the 
five  hydrates  just  enumerated.  The  first  two  of  these  are 
commercial  product-,  :m<l  have,  important  applications  in  tin; 
arts.  They  .-ill  differ  from  the  hydrates  of  other  metals  in  that 
they  cannot  he  decomposed  hy  heat  alone. 

A^ain,  if  we  net  on  water  with  calcium  or  magnesium,  we 
obtain  calcic  or  magnesic  hydrate;;  but  the  douMc  atom  of 
water  is  then  decomposed  by  these  bivalent  metals. 

//.  O,  IL  +   Ca  =  Ca-0,*ff.2  +  //  // 

Water.  Calcium.          Calcic  Hydrate.          Hydrogen  Oaf. 

//,  a,/^  _|_  Mg  =  Mg-OfJl,  +  ff-ff 

Wutcr.  MagncHluin.     Magnetic  Hydrate.      Hydrogen  Oai. 

These  two  hydrates,  as  well  as  those  of  the  allied  metals, 
barium  and  strontium,  although  much  less  soluble  in  water 
than  the  alkalies,  still  dissolve  in  this  common  solvent  to  a 
limited  extent,  and  manifest  decided  caustic  qualities.  When 
dry  they  have  an  earthy  appearance,  and  hence  are  frequently 
known  as  the  alkaline  earths.  They  also  differ  from  the  true 
alkalies  in  the  fact  that,  they  are  readily  decomposed  by  heat  ; 
and  since  they  are  then  resolved  into  water  and  a  metallic 
oxide,  as  the  following  reaction  shows,  the  opinion  formerly 
entertained  in  regard  to  their  composition  was  not  unnatural. 


II,  n  [44] 

When  heated. 

Moreover,  when  the  anhydrous  oxides  are  mixed  with  water, 
they  enter  into  direct  union  with  a  portion  of  the  liquid.  This 
combination  is  usually  attended  with  the  evolution  of  great 
heat,  and  the  process  is  known  as  slaking. 

Ca  0  +  If*  0  =  Car-  OfH¥  [45] 

There  are  many  other  metallic  hydrates  which  are  still  more 

readily   decomposed  by  heat.     These,  as  a  rule,   cannot  be 

formed  by  the  direct  union  of  the  corresponding  metallic  oxide 

and   water,   but  may  be  obtained  by  adding  to  a  solution  of 

G 


82  BASES,  ACIDS,  AND  SALTS. 

a  salt   of  the   metal  one   of  the  soluble  hydrates  mentioned 
above.     Thus,  — 


(  Cu  G13  +  2Na-0-H+  Aq)  —  (  Cu=0.fH2  +  2Na  Cl  +  Aq) 

Cupric  Chloride.  Cupric  Hydrate.     Sodic  Chloride. 

[46] 
(ZnC!2  +  ZK-0-H+Aq)  =  (Zn-OfS,  +  1KCI  +  Aq) 

Zincic  Chloride.  Zincic  Hydrate.       Potassic  Chloride. 


erric  Chloride.  Ferric  Hydrate.       Baric  Chloride. 

The  hydrates  are  regarded  by  some  chemists  as  compounds 
of  the  metal  with  the  compound  radical  hydroxyl,  and  their 
symbols  are  then  written  after  a  simpler  type,  thus, — 

Ca-(ffO)2  Fe-(HO)2  [<>2]I(#0)6 

Calcic  Hydrate.  Ferrous  Hydrate.  Chromic  Hydrate. 

Ammonia.  —  Closely  allied  to  these  metallic  hydrates  is  a 
very  remarkable  compound,  formed  by  dissolving  ammonia 
gas,  JV7/3,  in  water.  Although  the  product  resembles,  in  many 
of  its  physical  relations,  a  simple  solution  of  gas  in  water,  yet 
the  compound  in  all  its  chemical  relations  acts  like  a  metallic 
hydrate, 


NH,      +      R20     = 

Ammonia  Gas.  Water.  Ammonic  Hydrate. 

which  has  led  chemists  to  write  its  symbol  after  the  type  of 

water,  and  to  assume  the  existence  of  a  univalent  compound 

i 
radical  NH±,  to  which  has  been  given  the  name  of  ammonium. 

Metallic  Oxides  or  Basic  Anhydrides.  —  Closely  allied  to 
the  metallic  hydrates,  in  the  relation  we  are  now  considering, 
are  many  of  the  simple  compounds  of  the  metals  with  oxygen 
which  are  called  in  general  metallic  oxides.  Such  compounds 
as 

Ca-0         Ba-0         Pb=0         Fe-0         Gu-0         Aa.2=0 

Calcic  Oxide.      Baric  Oxide.    Plumbic  Oxide.  Ferrous  Oxide.  Cupric  Oxide.  Argentic  Oxide. 

may  be  regarded  as  formed  from  one  or  more  molecules  of  water, 
by  replacing  all  the  atoms  of  hydrogen  with  those  of  some  metal ; 
and  these  oxides  as  well  as  the  hydrates  before  mentioned  are 
frequently  classed  together  under  the  common  title  of  bases. 
although  it  would  be  best  to  confine  this  term  to  the  metallic 


BASES,  ACIDS,  AND  SALTS.  83 

hydrates  alone,  and  to  distinguish  the  basic  oxides  as  basic 
anhydrides.  (37) 

Salts.  —  The  atoms  of  hydrogen  still  remaining  in  a  metallic 
hydrate  may  be  replaced  with  the  atoms  of  a  well-defined  class 
of  non-metallic  elements  and  compound  radicals ;  and,  for  a 
reason  which  will  soon  appear,  the  replacing  atoms  are  called 
acid  or  negative  radicals.1 

From  this  replacement  results  a  new  class  of  compounds  we 
call  salts.  Thus,  — 

K-O-H  gives  K-O-Cl,     also  K-0-N02  and  K-0-(C2ff30) 

Potassic  Hydrate.       Potassic  Hypochlorite.          Potassic  Nitrate.  Potassic  Acetate. 

Ca-OfK2  gives    Ca-0.rS0.2    Ca=OfCO    Ca=0,=(C2ff30)2 

Calcic  Hydrate.  Calcic  Sulphate.     Calcic  Carbonate.  Calcic  Acetate.     ' 

36.  Acids.  —  Opposed  in  chemical  properties  to  the  so- 
called  bases  is  another  very  important  class  of  compounds 
called  acids.  They  derive  their  name  from  the  fact  that  they 
are  generally  soluble  in  water  and  have  a  sharp  or  sour  taste, 
although  there  are  many  exceptions  to  the  rule.  Like  the 
bases,  they  all  contain  hydrogen  ;  but  this  hydrogen  can  no 
longer  be  replaced  by  non-metallic  elements  or  negative  radi- 
cals, but  only  by  metallic  elements  and  positive  radicals,  and  it 
is  herein  that  the  chief  distinction  lies.  Moreover,  the  opposi- 
tion of  these  two  classes  of  compounds  also  appears  in  the  fact 
that,  while  in  bases  the  replaceable  hydrogen  atoms  are  united 
to  a  metallic  atom  or  positive  radical,  which  for  this  reason  we 
frequently  call  a  basic  radical,  in  the  acids,  on  the  other  hand, 

1  The  word  radical,  as  used  in  chemistry,  stands  for  any  atom  or  group  of 
atoms,  which  is,  for  the  moment,  regarded  as  the  principal  constituent  of  the 
molecules  of  a  given  compound,  and  which  does  not  lose  its  integrity  in  the 
ordinary  chemical  reactions  to  which  the  substance  is  liable.  The  distinc- 
tion between  basic  and  acid  radicals  (or  positive  and  negative  radicals  as  they 
are  more  frequently  called)  will  become  clear  as  we  advance.  It  is  sufficient 
for  the  present  to  state  that,  although  these  terms  imply  an  opposition  of  rela- 
tions rather  than  a  difference  of  qualities,  yet,  as  a  general  rule,  the  metallic 
atoms  are  basic  radicals,  while  the  non-metallic  atoms  are  acid  radicals. 
Moreover  it  may  be  added,  that  among  compound  radicals  those  consisting  of 
carbon  and  hydrogen  alone  are  usually  basic,  and  those  containing  also  oxy- 
gen usually  acid ;  and,  further,  that  of  the  two  most  important  radicals  con- 
taining nitrogen,  ammonium  (Nfft)  is  strongly  basic,  and  cyanogen  ( CN)  as 
decidedly  acid.  In  this  book,  with  few  exceptions,. the  basic  radicals  are 
always  placed  on  the  left-hand,  and  the  acid  radicals  on  the  right-hand  side, 
of  the  molecular  symbols. 


84  BASES,  ACIDS,  AND  SALTS. 

these  same  hydrogen  atoms  are  united  as  a  rule  to  a  non- 
metallic  atom  or  negative  radical,  frequently,  also,  called  as 
above  an  acid  radical.  In  most  cases  there  is  a  vinculum 
which  unites  the  two  parts  of  the  molecule  ;  and  both  in  acids 
and  in  bases  this  vinculum  consists  usually  of  one  or  more 
oxygen  atoms,  although  in  a  large  class  of  acids  the  hydrogen 
atoms  are  united  directly  to  the  radical  without  any  such  con- 
nection. The  acids  of  this  class  have  by  far  the  simplest 
constitution  ;  and  we  will  give  examples  of  these  first,  adding 
in  each  case  a  reaction  to  illustrate  the  acid  relations  of  the 
compound.  In  studying  these  reactions,  it  must  be  borne  in 
mind  that  the  evidence  of  acidity  is  in  each  case  to  be  found  in 
the  fact  that  one  or  more  of  the  hydrogen  atoms  of  the  com- 
pound may  be  replaced  by  positive  radicals  or  metallic  atoms. 
This  replacement  may  be  obtained  in  one  of  four  ways,  —  by 
acting  on  the  acid,  either  with  the  metal  itself,  or  with  a  metallic 
oxide,  or  with  a  metallic  base,  or  with  a  metallic  salt. 

(2HCI  +  Aq)  +  NaNa  =  (2  Na  Cl  +  Aq)  +  HI-HI 

Hydrochloric  Acid.  Sodium.          Sodic  Chloride. 

(2HCl  +  Aq)  +  ZnO   =    (ZnCl2   +   R20  +  Aq) 

Zincic  Oxide.       Zincic  Chloride. 

[47] 
(HBr    +    K-O-H  -\-  Aq)  =  (KBr  + 

Hydrobromic  Acid.    Potassic  Hydrate.  Potessic  Bromide. 


(JSI+  Ag-0-N02  +  Aq)  =  Agl  +  (ff- 

Hydriodic  Acid.    Argentic  Nitrate.  Argentic  Iodide.          Nitric  Acid 

We  will  next  give  examples  of  more  complex  acids,  in  which 
the  two  parts  of  the  molecule  are  united  by  a  vinculum  of  oxy- 
gen atoms. 

(H-0-(CZHS0)  4-  Na-0-H4-  Aq)  =  (Na-0-(  C2H30)  -4-H204-Aq) 

Acetic  Acid.  Sodic  Hydrate.  Sodic  Acetate. 


4-  Cu°  =   (Cu=OfSOa  -f-  H,0  -f  Aq) 

Sulphuric  Acid.  Cupric  Oxide.        Cupric  Sulphate. 

(H3=0,=PO  -f   SK-O-H  -f  Aq)  =   (K^O^PO  +  3H,0  -f  Aq) 

Phosphoric  Acid.       Potassic  Hydrate.  Potassic  Phosphate. 

Such  acids  as  these  are  called  oxygen  acids.  Like  the 
hydrates,  they  may  be  regarded  as  compounds  of  hydroxyl, 
but  with  negative  instead  of  positive  radicals,  thus  :  — 


BASES,  ACIDS,  AND  SALTS.  85 


ffO-N02 

Nitric  Acid.  Sulphuric  Acid.  Phosphoric  Acid. 

This  mode  of  writing  the  symbols  is  not  only  frequently  con- 
venient, but  has  been  of  real  value  by  bringing  out  unex- 
pected and  important  relations.  It  does  not,  however,  indicate 
any  fundamental  difference  of  opinion  in  regard  to  the  consti- 
tution of  these  hydrates,  and  this  at  once  appears  when  the 
symbols  are  put  into  the  graphic  form. 

When  an  acid,  like  acetic  acid,  contains  but  one  atom  of  hy- 
drogen, which  is  replaceable  by  a  metallic  atom  or  a  positive 
radical,  it  is  called  monobasic  ;  when,  like  sulphuric  acid,  it  con- 
tains two  such  hydrogen  atoms,  it  is  called  dibasic  ;  when,  like 
phosphoric  acid,  it  contains  three,  it  is  tribasic,  &c.  Moreover, 
one  evidence  of  this  difference  of  basicity  is  found  in  the  fact 
that  whereas  a  monobasic  acid  can  only  form  one  salt  with  a 
univalent  radical,  a  dibasic  acid  can  form  two,  and  a  tribasic 
three.  Thus,  while  we  have  only  one  sodic  nitrate,  there  are 
two  sodic  sulphates  and  three  sodic  phosphates. 


Na-0-N0.2 

Sodic  Nitrate.  Acid  Sodic  Phosphate. 


H,Na-0.rS02 

Acid  Sodic  Sulphate.  Neutral  Sodic  Phosphate. 


Neutral  Sodie  Sulphate.  Basic  Sodic  Phosphate. 

There  is,  however,  but  one  calcic  sulphate,  for,  since  the  cal- 
cium atoms  are  bivalent,  a  single  one  is  sufficient  to  replace 
both  of  the  hydrogen  atoms  in  the  acid. 

37.  Acid  Anhydrides.  —  Besides  the  acids  properly  so  called, 
all  of  which  contain  hydrogen,  there  is  another  class  of  com- 
pounds which  bear  the  same  relation  to  the  true  acids  which  the 
metallic  oxides  bear  to  the  true  bases.  To  avoid  confusion,  com- 
pounds of  this  class  have  been  distinguished  as  anhydrides^  and 
they  may  be  regarded  as  one  or  more  molecules  of  water  in 
which  all  the  hydrogen  has  been  replaced  by  negative  or  acid 
radicals.  As  among  the  most  important  of  these  we  may 
enumerate  Sulphuric  Anhydride  S0.2=0  or  S03,  Nitric  Anhy- 


1  More  precisely  acid  anhydrides,  but  as  the  basic  anhydrides  are  usually 
called  simply  metallic  oxides,  the  qualifying  term  is  seldom  added. 


86  BASES,  ACIDS,  AND  SALTS. 

dride  (N02)2=0  or  NZ0#  Carbonic  Anhydride  00=0  or  C02, 

i 
Phosphoric  Anhydride  (P02)2=0  or  P205,  and  Silicic  Anhy- 

IV 

dride  /Si=02.  Most  of  the  anhydrides  unite  directly  with 
water  to  form  acids,  and  several  of  the  acids,  when  heated, 
give  off  water  and  are  resolved  into  anhydrides.  [Compare 
44  and  45.] 

H20    +     S03  = 


3ff20    +    P205  = 

[49] 
fffOfSi  =  SiOa  +     2ff20 

Silicic  Acid.     Silicic  Anhydride. 


=  R203  +    3ff20 

Boric  Acid.  Boric  Anhydride. 

Moreover  in  many  cases  these  anhydrides  will  combine  di- 
rectly with  the  metallic  oxides  to  form  salts  ;  and  the  reac- 
tions are  best  indicated  by  a  rational  formula,  which  represents 
the  oxide  and  anhydride  as  radicals  in  the  resulting  compound. 
Thus,  baric  oxide  burns  in  the  vapor  of  sulphuric  anhydride, 
yielding  baric  sulphate  ;  and  lime  also  unites  directly  with  the 
same  anhydride,  although  with  less  energy,  forming  calcic  sul- 
phate. 

BaO  +  S03  =  BaO,  S03  and  CaO  +  S03  =  CaO,  S03 

We  are  thus  led  to  the  old  formulae  of  the  dualistic  system, 
according  to  which  the  metallic  oxides  were  the  only  true 
bases,  the  anhydrides  were  the  only  true  acids,  and  the  two 
wrere  regarded  as  paired  in  all  true  salts.  But,  although  in 
its  modern  theories  our  science  has  fortunately  left  the  ruts  to 
which  the  dualistic  ideas  for  so  long  limited  its  progress,  yet  it 
must  be  remembered,  that,  according  to  our  present  definitions, 
these  dualistic  formulae  are  perfectly  legitimate,  and  still  give 
the  simplest  exposition  of  a  large  number  of  important  facts. 

38.  Salts.  —  The  definition  of  the  term  "salt"  has  been  clearly 
implied  in  the  definitions  of  "base"  and  "acid"  already  given. 
It  is  any  acid  in  which  one  or  more  atoms  of  hydrogen  have 
been  replaced  with  metallic  atoms  or  basic  radicals  ;  it  is  any 
base  in  which  the  hydrogen  atoms  have  been  more  or  less  re- 
placed by  non-metallic  atoms  or  acid  radicals  ;  or  it  may  be  the 


BASES,  ACIDS,  AND   SALTS.  87 

product  of  the  direct  union  of  a  metallic  oxide  and  an  anhy- 
dride. A  neutral  salt  is,  properly  speaking,  one  in  which  all 
the  hydrogen  atoms,  whether  of  base  or  acid,  have  been  re- 
placed as  just  stated.  A  basic  salt  is  one  in  which  one  or 
more  of  the  hydrogen  atoms  of  the  base  remain  undisturbed, 
and  therefore  still  capable  of  replacement  by  acid  radicals.  An 
acid  salt  is  one  in  which  one  or  more  of  the  hydrogen  atoms  of 
the  acid  remain  undisturbed,  and  therefore  capable  of  replace- 
ment by  basic  radicals. 

But,  besides  the  basic  and  acid  salts,  which  come  under  these 
definitions,  there  are  also  others  which  can  be  most  simply  de- 
fined as  consisting  of  several  atoms  of  the  metallic  oxide  to  one 
of  anhydride,  or  of  several  atoms  of  anhydride  to  one  of  the 
metallic  oxide. 

As  an  example  of  acid  salts  of  the  second  class  we  have,  be- 
sides the  two  sodic  sulphates  mentioned  on  page  85,  also  a 
third,  which  may  be  written  Na20,2S03.  This  is  easily  ob- 
tained by  simply  heating  the  acid  sulphate. 


=  Na.20,  2S03  +  I$1M          [50] 

Acid  Sodic  Sulphate.  Sodic  Bisulphate.  Water. 

If  heated  to  a  still  higher  temperature,  one  atom  of  the  anhy- 
dride is  set  free,  and  the  salt  falls  back  into  the  neutral  sul- 
phate. 


S03    + 

Bisulphate.  Neutral  Sulphate.  Anhydride. 

This  reaction  justifies  the  dualistic  form  given  to  the  symbol; 
but  other  relations  of  the  bisulphate  may  be  better  expressed 
by  the  following  typical  formula,  — 


Sodic  Bisulphate.  Neutral  Sulphate.  Anhydride. 

in  which  a  group  of  two  atoms  of  SO&  soldered  together  by 
one  atom  of  oxygen,  acts  as  a  bivalent  radical. 

As  an  example  of  a  basic  salt  of  the  second  class  we  have, 
in  addition  to  the  two  plumbic  acetates  of  the  normal  type, 

Pb-  Of(  CA  0)2          and          Pb=  Of(  C2ffs  0),  H 

Neutral  Plumbic  Acetate.  Basic  Plumbic  Acetate. 


88  BASES,  ACIDS,  AND   SALTS. 

a  third  salt  containing  three  times  as  much  lead,  — 

(Pb-0-Pb-0-Pb)  =  02=(C2ff30)2,  [51] 

Triplumbic  Acetate. 

in  which  a  group  of  three  atoms  of  lead,  soldered  together  by 
two  atoms  of  oxygen,  acts  as  a  bivalent  radical.  It  is  evident 
that,  theoretically,  any  number  of  multivalent  radicals  might  be 
united  in  this  way,  and  also  that  the  complex  radical  thus 
formed  will  have  a  quantivalence  easily  determined  by  esti- 
mating the  number  ( f  bonds  which  remain  unsatisfied ;  but, 
practically,  the  grouping  cannot  be  carried  to  a  very  great  ex- 
tent, for  the  stability  of  the  radical  diminishes  with  its  com- 
plexity, and  a  condition  is  soon  reached  when  it  can  no  longer 
sustain,  if  we  may  so  express  it,  its  own  weight.  Moreover, 
while  some  radicals,  like  the  atoms  of  lead,  copper,  mercury, 
and  iron,  are  prone  to  group  themselves  in  this  way,  the  larger 
number  show  but  little  tendency  to  this  mode  of  union. 

The  symbols  of  these  acetates  may  also  be  written  on  the 
dualistic  type,  which  represents  them  as  compounds  of  plumbic 
oxide,  Pb  0,  and  acetic  anhydride,  (74//6  03.  We  have,  then,  — 

PbO,  04ff,03        and         3PbO,  C4ff«03          [52] 

Neutral  Plumbic  Acetate.  Triplumbic  Acetate. 

and  we  may  thus  best  illustrate  the  important  fact  that  the 
second  compound  is  prepared  by  combining  with  the  first  an 
additional  quantity  of  plumbic  oxide. 

It  will  appear  on  reviewing  the  symbols  of  the  acids,  base?, 
and  salts  given  in  this  section,  that,  in  by  far  the  greater  num- 
ber, the  two  parts  of  the  molecule  are  held  together  by  one  or 
more  atoms  of  oxygen,  which  act  as  a  vinculum.  Such  com- 
pounds are  called  oxygen  salts,  using  the  word  salt,  as  is  fre- 
quently done,  to  stand  for  acids  and  bases,  as  well  as  for  the 
true  metallic  salts;  and  in  fact  they  all  belong  to  the  same 
type  of  chemical  compounds.  Since  oxygen  plays  so  impor- 
tant a  part  in  terrestrial  nature,  we  might  well 'expect  that 
these  oxygen  compounds  would  hold  a  very  conspicuous  place 
in  our  chemical  science,  —  and  such  is  indeed  the  fact.  Dur- 
ing the  dualistic  period  the  study  of  chemistry  was  almost 
wholly  confined  to  the  oxygen^  compounds,  and,  even  no\v, 
they  occupy  by  far  the  largest  share  of  a  che:ni>t's  attention. 


BASES,  ACIDS,  AND  SALTS.  89 

There  is,  however,  another  element,  namely,  sulphur,  which 
is  capable  of  filling  the  place  occupied  by  oxygen  in  many 
of  its  compounds,  and  thus  may  be  formed  a  distinct  class  of 
bodies  which  are  called  sulphur  salts.  These  compounds  are 
not  nearly  so  numerous  as  the  oxygen  salts,  and  have  not  been 
so  well  studied,  so  that  a  few  examples  will  be  sufficient  to 
illustrate  their  general  composition,  and  the  relations  which 
they  bear  to  the  corresponding  oxygen  compounds. 

Oxygen  Salts.  Sulphur  Salts. 

H-O-H  H-S-H 

Water  or  Hydric  Acid.  Sulphohydric  Acid. 

K-O-H  K-S-H 

Potassic  Hydrate.  Potassic  Sulphohydrate. 

KrO.rCO  KfSfCS 

Potassic  Carbonate.  Potassic  Sulphocarbonate. 

39.  Test-Papers.  —  The  soluble  bases  and  acids,  when  dis- 
solved in  water,  cause  a  striking  change  of  color  in  certain 
vegetable  dyes,  and  these  characteristic  reactions  give  to  the 
chemist  a  ready  means  of  distinguishing  between  these  two 
important  classes  of  compounds.  The  two  dyes  chiefly  used 
for  this  purpose  are  turmeric  and  litmus,  and  strips  of  paper 
colored  with  the  dyes  are  employed  in  testing.  Turmeric 
paper,  which  is  naturally  yellow,  is  turned  brownish  red  by 
bases,  while  litmus  paper,  which  is  naturally  blue,  is  turned 
red  by  acids,  and  in  both  cases  the  natural  color  is  restored  by 
a  compound  of  the  opposite  class. 

If  to  a  solution  of  a  strong  base,  like  sodic  hydrate,  we  add 
slowly  and  carefully  a  solution  of  a  strong  acid,  like  sulphuric, 
we  shall  at  last  reach  a  condition  in  which  the  solution  affects 
neither  test-paper,  and  it  is  then  said  to  be  neutral.  On  evap- 
orating this  solution  we  obtain  a  neutral  salt,  like  sodic  sulphate, 
and  the  presence  in  the  solution  of  the  slightest  excess  of  acid 
or  base  beyond  the  amount  required  to  form  this  salt  would 
have  been  made  evident  by  the  test-papers.  Tn  such  cases,  we 
may  therefore  use  these  test-papers  to  distinguish  between  acid, 
basic,  and  neutral  salts,  but  only  with  great  caution ;  for  we  find 
that  when,  as  in  acid-carbonate  of  soda,  a  strong  base  is  asso- 
ciated with  a  weak  acid,  the  reaction  is  still  basic,  although 


90  BASES,  ACIDS,  AND  SALTS. 

the  acid  may  be  greatly  in  excess,  and,  on  the  other  hand, 
when,  as  in  cupric  sulphate,  a  weak  base  has  been  associated 
with  a  strong  acid,  the  reaction  may  be  strongly  acid  even  in 
the  basic  salts.  The  explanation  of  these  apparent  anomalies 
is  to  be  found  in  the  fact  that  these  colored  reagents  are  all 
salts  themselves,  and  the  reactions  examples  of  metathesis. 
The  coloring  matter  of  these  dyes  is  an  acid  which  varies  its 
tint  according  as  the  hydrogen  atoms  have  or  have  not  been 
replaced ;  and  when,  for  any  reason,  the  acid  or  base  of  the  salt 
examined  is  not  in  a  condition  to  determine  the  necessary  me- 
tathesis, the  characteristic  change  of  color  does  not  take  place. 

Unfortunately,  the  facts  just  stated  have  led  to  great  confu- 
sion in  the  use  of  the  words  "acid"  and  "basic"  as  applied  to 
salts,  since  these  terms  sometimes  have  reference  solely  to  the 
number  of  atoms  of  hydrogen,  in  the  acid  or  base,  which  have 
not  been  replaced  in  the  formation  of  the  salt,  and  at  other  times 
refer  to  the  reactions  of  the  salt  on  the  colored  reagents  just 
described.  A  confusion  of  this  sort  must  have  been  noticed  in 
the  names  of  the  three  phosphates  of  soda  on  page  85.  The 
so  called  neutral  phosphate  is  theoretically  an  acid  salt,  and 
the  basic  phosphate  a  neutral  salt,  but  the  salts  give  with  test- 
papers  the  reactions  which  their  names  indicate.  The  theo- 
retical is  the  only  legitimate  use,  and  the  one  we  shall  adhere 
to  in  this  book,  except  in  regard  to  names  of  compounds  which 
cannot  be  arbitrarily  changed. 

40.  Alcohols,  Fat  Acids,  Ethers.  —  The  hydrocarbon  radicals 
mentioned  in  §  34  yield  a  very  large  number  of  compounds 
after  the  type  of  water,  which  are  closely  allied  to  the  hy- 
drates and  anhydrides,  both  acid  and  basic,  just  described.  Jf 
one  of  the  hydrogen  atoms  in  the  molecule  of  \iater  is  replaced 
by  either  of  the  univalent  basic  radicals,  methyl,  ethyl,  propyl, 
&c.,  we  obtain  a  class  of  compounds,  called  alcohols,  of  which 
our  common  alcohol  is  the  most  important.  On  the  other 
hand,  if  the  atom  of  hydrogen  is  replaced  by  one  of  the  uni- 
valent acid  radicals,  formyl,  acetyl,  propionyl,  &c.,  we  obtain  an 
important  class  of  acid  compounds,  of  which  acetic  acid  (vine- 
gar) is  the  best  known,  but  which  also  includes  a  large  number 
of  fatty  substances  closely  related  to  our  ordinary  fats.  Hence 
the  name  Fat  Acids,  by  which  this  class  of  compounds  is  gen- 
erally designated. 


BASES,  ACIDS,  AND  SALTS.  91 

Basic  Hydrates  or  Alcohols. 

Methylic  Alcohol  (wood  spirits)  CH^O-H. 

Ethylic  Alcohol  (common  alcohol)  C2ff5-0~H. 

Propylic  Alcohol  C3H7-Q-H. 

Butylic  Alcohol  C4H,-0-ff. 

Amylic  Alcohol  (fusel  oil)  C.H^-O-H. 

(With  six  others  already  known.) 

Acid  Hydrates,  Fat  Acids. 
Formic  Acid  H-O-CHO. 

Acetic  Acid  H-0-Q&O. 

Propionic  Acid  H~  0  -  C3H5  0. 

Butyric  Acid  E-  0-  C4E7  0. 

Valerianic  Acid  H-  0-  G&ff9  0. 

(With  fifteen  others  already  known.) 

If  now  we  replace  both  of  the  hydrogen  atoms  of  water  by 
the  same  basic  radicals  mentioned  above,  we  obtain  a  class  of 
compounds  called  ethers,  which  correspond  to  the  metallic 
oxides  or  basic  anhydrides;  and  if  we  replace  the  two  hydro- 
gen atoms  by  the  corresponding  acid  radicals,  we  obtain  a 
similar  series  of  acid  anhydrides.  Lastly,  if  we  replace  one  of 
the  hydrogen  atoms  by  a  basic  radical,  and  the  other  by  an 
acid  radical,  we  get  a  class  of  compounds  also  called  ethers 
(but  distinguished  as  compound  ethers),  which  correspond  to 
the  salts. 

Examples  of  Anhydrides. 

1.  Simple  Ethers. 

Methylic  Ether  CE3~0-CE3    or  (CH3}2=0. 

Ethylic  Ether  (common  ether)  C2H5-Q-C2H5  or  (O2H5)2=0. 

2.  Mixed  Ethers. 

Methyl-ethyl  Ether  CHS-0-  O2H5. 

Ethy  1-amyl  Ether  C2E5-  0  -  C5HU. 

3.  Compound  Ethers. 

Acetic  Ether  C.2E5-  0-  C,R.  0. 

Butyric-methyl  Ether  CE3-Q-C4E70. 

4.  Acid  Anhydrides. 

Acetic  Anhydride  C.2H^  0~0~  CM*  0  or  ( C*E3  0).,=  0. 

Valerianic  Anhydride      C5H»0-0-C5H,0  or  (C5H,0)iO. 


92  BASES,  ACIDS,  AND  SALTS. 

The  positive  radicals,  of  which  the  alcohols  consist,  hold  an 
intermediate  position  between  the  strong  basic  radicals  on  the 
one  hand,  and  the  strong  acid  radicals  on  the  other,  and  the 
same  is  true  of  the  alcohols  themselves,  which  hold  a  middle 
place  between  the  strong  basic  and  the  strong  acid  hydrates. 
This  is  indicated  by  the  following  reactions  ;  in  what  way  it  is 
left  to  the  student  to  inquire. 


H-H 
2  CH3~0-H+  HfOfSOi 


41.  Glycols.  —  The  class  of  hydrates  described  in  the  last  sec- 
tion belong  to  the  simple  type  of  water.  But  we  have  also  a  class 
of  analogous  compounds  belonging  to  the  type  of  water  doubly 
condensed.  If  in  the  double  molecule  of  water  (H.f  02=H2)  we 
replace  one  of  the  pairs  of  hydrogen  atoms  by  either  of  the 
bivalent  positive  radicals,  ethylene,  propylene,  butylene,  &c., 
we  obtain  a  series  of  compounds  closely  resembling  the  alco- 
hols, called  glycols,  and  by  substituting  the  related  negative 
radicals  we  obtain  two  series  of  acid  hydrates,  which  stand  in 
the  same  relation  to  the  glycols  that  the  fat  acids  bear  to  the 
alcohols.  These  relations  are  shown  in  the  following  scheme, 
which,  however,  includes  only  the  five  first  members  of  each 
of  these  three  series  of  compounds.  It  should  be  noticed  in 
this  connection  that  each  of  the  bivalent  positive  radicals  yields 
two  related  negative  radicals,  while  the  univalent  positive  radi- 
cals of  the  last  section  yield  only  one  such  negative  radical  ; 
and  moreover  that  the  acids  in  the  first  series,  although  dia- 
tomic, are  only  monobasic,  while  those  in  the  second  series  are 
both  diatomic  and  dibasic  (43). 


Ethylic  Glycol.  Glycolic  Acid.  Oxalic  Acid. 


Propylic  Glycol.  Lactic  Acid.  Malonic  Acid. 


H2=02=C4fI402 

Butylic  Glycol.  Oxybutyric  Acid.  Succinic  Acid. 


Amylic  Glycol.  Valerolactic  Acid.  Pyrotartaric  Acid. 

efftfOfH,  HfOfC,HwO  Hf02=C6ffs0 

Hexyl  Glycol.  Leucic  Acid.  Adipic  Acid. 


BASES,  ACIDS,  AND   SALTS.  93 

Corresponding  to  these  basic  and  acid  hydrates  we  have 
also  been  able  to  obtain  in  several  cases  the  basic  and  acid 
anhydrides,  besides  a  very  large  number  of  compound  ethers. 

42.  Glycerines  and  Sugars.  —  In  the  alcohols  one  hydrogen 
atom  from  the  original  typical  molecule  (typical  hydrogen]  re- 
mains undisturbed.     In  the  glycols  there  are  two  such  hydro- 
gen atoms,  and  hence  these  compounds  are  frequently  called 
diatomic  alcohols.     Our  common  glycerine  is  a  triatomic  alco- 
hol, and  may  be  regarded  as  formed  from  a  molecule  of  water 
trebly  condensed  (H^O^HZ),  by  replacing  one  of  the  groups  of 
hydrogen  atoms  with  the  trivalent  radical  glyceryl  (C3H5).     It 
is  probable  that  a  large  number  of  triatomic  alcohols  or  glycer- 
ines may  hereafter  be  obtained,  but  only  two  are  now  known. 

Propylic  Glycerine  (common  glycerine) 
Amylic  Glycerine 

From  the  glycerines  we  may  derive  acids,  anhydrides,  and 
compound  ethers,  bearing  to  each  other  the  same  relations  as 
those  derived  from  the  alcohols  of  a  lower  order,  but  only  a 
few  of  the  possible  compounds  which  our  theory  would  foresee 
are  yet  known.  The  natural  fats  are  compounds  of  glycerine 
with  the  fat  acids,  and  it  is  probable  that  our  common  sugars 
are  likewise  derived  from  alcohols  of  a  still  higher  order  of 
atomicity. 

43.  Atomicity  and  Basicity  of  an  Acid.  —  By  the  atom- 
icity of  a  compound  is  meant  the  number  of  hydrogen  atoms 
which  it  retains  from  the  original  typical  molecule  still  unre- 
placed,  and  the  use  of  this  term  with  reference  to  the  basic 
hydrates  has  been  already  abundantly  illustrated  in  this  chap- 
ter.    In  the  case  of  the  acids  a  distinction  must  be  made  be- 
tween atomicity  and  basicity,  which  is  frequently  important. 

The  formula  of  every  acid  may  be  written  on  the  type  of  one 
or  more  atoms  of  hydrochloric  acid,  as  Hn  7?n,  in  which  Hn  stands 
for^the  replaceable  atoms  of  hydrogen,  and  Jt*  for  all  the  rest 
of  the  atoms  of  the  molecule,  which  may  be  regarded  as  forming 

a  radical  with  an  atomicity  equal  to  the  number  of  replaceable 

i  n  in 

hydrogen  atoms.    The  symbols  H-NOS  HfSO±  fffPO*  are 


94  BASES,  ACIDS,  AND  SALTS. 

written  on  this  principle.  In  each  case  the  acid  is  said  to 
have  the  atomicity  of  the  radical.  The  basicity  of  the  acid, 
on  the  other  hand,  depends,  not  on  the  total  number  of  replace- 
able hydrogen  atoms,  but  on  the  number  which  may  be 
replaced  by  metallic  atoms  or  basic  radicals.  As  a  general 
rule,  it  is  true  that  the  basicity  is  the  same  as  the  atomicity, 
but  this  is  not  always  the  case.  Thus  lactic  acid  is  diatomic 
but  monobasic,  and  the  same  is  true  of  the  other  acids  homol- 
ogous with  it  (page  92). 

ff,  H=(C3ff403)    Na,H=(C8HA)     Na,  (C7ff5 

Lactic  Acid.  Sodic  Lactate.  Sodic  Benzolactate 


K,  C2ff/(  03H4  03)         CZH6,  C,H^(  C3ff4  03) 

Potassic  Ethyl-lactate.  Diethylic-lactate. 


Only  one  atom  of  hydrogen  can  be  replaced  by  a  metallic 
radical,  but  a  second  may  be  replaced  by  either  a  negative  or 
an  alcoholic  radical,  as  in  the  last  three  symbols,  and  in  desig- 
nating the  atoms,  thus  differently  related  to  the  molecular  struc- 
ture, it  is  usual  to  call  the  first  basic  and  the  other  alcoholic 
hydrogen. 

We  might,  in  like  manner,  distinguish  between  the  atomicity 
and  the  acidity  of  a  base,  but  this  distinction  has  not  been  found 
as  yet  to  be  of  practical  importance. 

44.  Water  of  Crystallization.  —  Among  the  most  striking  char- 
acteristics of  the  class  of  compounds  we  call  salts  is  their  sol- 
ubility in  water  and  their  tendency  on  separating  from  it, 
in  consequence  of  either  the  evaporation  or  the  cooling  of 
the  fluid,  to  assume  definite  crystalline  forms.  These  crys- 
tals, as  a  general  rule,  are  complex  crystalline  aggregates  of 
molecules  of  the  salt  and  molecules  of  water.  The  water  is 
held  in  combination  by  a  comparatively  feeble  force,  and  may 
be  generally  driven  off  by  exposing  the  salt  to  the  temperature 
of  100°  C.,  when  the  crystals  fall  to  powder.  Sometimes  it'es- 
capes  at  the  ordinary  temperature  of  the  air,  when  the  crystals, 
as  before,  fall  to  powder  and  are  said  to  effloresce.  It  thus  evi- 
dently appears  that  the  water,  although  an  essential  part  of  the 
crystalline  structure,  is  not  inherent  in  the  chemical  molecule, 
and  hence  the  name  Water  of  Crystallization.  The  presence  of 


BASES,   ACIDS,   AND   SALTS.  95 

water  of  crystallization  in  a  salt  is  expressed  by  writing  after 
the  symbol  of  the  salt,  and  separated  from  it  by  a  period,  the 
number  of  molecules  of  water  with  which  each  salt  molecule 
is  associated.  Thus  we  have 


FeSOJHtO 

Crystallized  Ferrous  Sulphate  or  Green  Vitriol.       Crystallized  Sodic  Carbonate  or  Sal  Soda. 

The  same  salt,  when  crystallized,  at  different  temperatures 
not  unfrequently  combines  with  different  amounts  of  water  of 
crystallization,  the  less  amounts  corresponding  to  the  higher 
temperatures.  Thus  manganous  sulphate  may  be  crystallized 
with  three  different  amounts  of  water  of  crystallization.  We 
have 

MnSO±.7H20  when  crystallized  below  6°  C. 
MnSO^H^O      "  u          between  7°  and  20°. 

MnSO^AH^O      "  "  between  20°  and  30°. 

The  crystalline  forms  of  these  three  compounds  are  entirely 
different  from  each  other  ;  and  this  fact  again  corroborates  the 
view  that  the  molecules  of  water,  while  a  part  of  the  crystalline 
structure,  are  not  a  part  of  the  chemical  type  of  the  salt.  It 
will  be  well  to  distinguish  the  molecular  aggregate,  which  the 
symbols  of  this  section  represent,  from  the  simpler  chemical 
molecules  by  a  special  term,  and  we  propose  to  call  them  crys- 
talline molecules.  While,  however,  there  is  little  room  for 
difference  of  opinion  in  regard  to  the  relations  in  which  the 
molecules  of  water  stand  to  the  structure  of  most  crystals,  there 
are  cases  where  the  condition  is  apparently  far  less  simple,  and 
where  we  find  the  water  so  firmly  bound  to  the  salt  itself  that 
it  seems  to  form  a  part  of  its  atomic  structure. 

Questions   and  Problems. 

1.  Analyze  reactions  [42].     Show  what  is  meant  by  a  metallic 
hydrate,  and  define  the  term  alkali.     Write  the  similar  reactions 
which  may  be  obtained  with  lithium,  caesium,  and  rubidium.    Name 
in  each  case  the  class  of  compounds  to  which  the  factors  and  pro- 
ducts belong.     Also  represent  these  reactions  by  graphic  symbols. 

2.  Analyze  reactions    [43].     State   the  distinction  between   an 
alkaline  earth  and  an  alkali,  and  write  the  similar  reactions  which 
may  be  obtained  with  barium  and  strontium.     Name  in  each  case 


96  BASES,  ACIDS,  AND  SALTS. 

the  class  of  compounds  to  which  the  factors  and  products  belong. 
Also  represent  the  reactions  by  graphic  symbols. 

3.  Analyze  reactions  [44]  and  [45],  and  write  the  similar  reac- 
tions which  may  be  obtained  with  either  of  the  metals,  calcium, 
strontium,  barium,  and  magnesium.     What  theory  of  the  constitution 
of  the  metallic  hydrates  do  these  reactions  suggest  V 

4.  In  what  respects  do  the  hydrates  Ca=  02  =  //2  and  Mg=  02=H2 
differ  from  K-O-H  and  Na-O-H  ? 

5.  Analyze  reactions  [46],  and  show  that  the  principal  products 
must  be  regarded  as  hydrates.     Name  the  class  of  compounds  to 
which  the  other  products  and  factors  belong. 

6.  State  the  third  theory  which  is  held  in  regard  to  the  constitu- 
tion of  the  hydrates,  and  write  the  symbols  of  the  different  hydrates 
according  to  this  view.     Also  bring  these  symbols  into  comparison 
with  those  of  the  same  compounds  written  after  the  other  two  plans, 
and  show  by  means  of  graphic  symbols  how  far  these  forms  are  arbi- 
trary, and  how  far  they  represent  fundamental  differences. 

7.  In  what  sense  may  the  solution  of  ammonia  gas  in  water  be 
regarded  as  an  hydrate  ?     Write  reactions  [46],  using  ammonic  hy- 
drate instead  of  the  hydrates  of  sodium,  potassium,  and  barium. 

8.  In  what  relation  do  the  metallic  oxides  stand  to  the  hydrates  ? 
Define  the  term  base. 

9.  Define  the  term  salt,  and  illustrate  your  definition  by  examples. 

10.  Define  the  term  acid.     How  does  an  acid  differ  from  a  me- 
tallic  hydrate  ?     Is  an  acid  necessarily  an  hydrate  ?      What  two 
classes  of  acids  may  be  distinguished  ? 

11.  What  is  the  distinction  between  an  acid  and  a  basic  radical. 
How  are  they  related  to  the  two  hydrogen  atoms  of  water  ?     As- 
suming that  there  is  no  difference  between  these  two  atoms  in  the 
original  molecule  of  water,  does  not  the  replacement  of  one  of  the 
atoms  by  a  radical  of  either  class  alter  the  relations  of  the  second  ? 
Is  there  not  an  analogy  between  these  phenomena  and  those  of 
magnetism  ? 

12.  Analyze  reactions  [47  et  seq.],  and  point  out  the  evidence  of 
acidity  in  each  case. 

13.  Analyze  the  following  reactions. 


K-O-H    +  HF  =   KF 

Ca-0.fH2  +  HfOfCO  =   Ca=0.fCO        +  2H,0 

Cu-02=E2  +  2H-0-NO,  =  Cu-0 


BASES,  ACIDS,  AND  SALTS.  97 

Na  Cl     +  Ef  0./SO,  =.  E,  Na-  Of  SO,  +  HI^l 
ZNaCl  +  H2=02=S02  =  Na2=02=S02      +  211101. 

Point  out  the  different  acids  and  bases.  In  what  does  the  evidence 
of  their  acidity  or  basicity  appear  either  in  these  or  in  reactions  pre- 
viously given  ?  Show  in  each  case  how  the  replacement  of  the  hy- 
drogen atoms  is  obtained,  and  illustrate  the  difference  between  the 
hydrogen  atoms  of  an  acid  and  those  of  a  base.  What  two  classes 
of  acids  may  be  distinguished  ? 

14.  Regarding  the  hydrates  as  compounds  of  hydroxyl,  how  can 
you  define  the  acids  and  bases  of  this  class  ? 

15.  Represent  the  composition  of  nitric,  sulphuric,  and  phosphoric 
acid  by  graphic  symbols,  and  show  that  the  two  modes  of  writing 
their  symbols  embody  essentially  the  same  idea. 

16.  Hydrochloric  acid,  acetic  acid,  nitric  acid,  hydriodic  acid,  hy- 
drobromic  acid,  sulphuric  acid,  carbonic  acid,  and  phosphoric  acid 
have  what  basicity  ?     Point  out,  in  the  various  reactions  given  in 
this  chapter,  the  evidence  in  each  case,  and  write  the  symbols  of  the 
possible  sodic  salts  of  the  different  acids. 

17.  What  class  of  compounds  do  the  symbols  S03,  ^V205,  P205, 
COy  and  Si02  represent  ?     By  a  comparison  of  symbols  show  how 
these  compounds  may  be  regarded  as  formed  from  water,  and  how 
they  are  related  to  the  corresponding  acids.     To  what  class  of  com- 
pounds do  they  stand  in  direct  antithesis  ? 

18.  Define  the  terms  basic  and  acid  hydrate  ;  basic  and  acid  an- 
hydride, and  compare  reactions  [49]  with  [44  and  45]. 

19.  Analyze  the  reaction,  BaO  -J-  S03  =  BaO,  S0y 

What  reason  may  be  urged  for  writing  the  symbol  of  baric  sulphate 
in  this  way  V  What  was  the  theory  of  the  dualistic  system  in 
regard  to  such  compounds  ?  Represent  the  symbol  by  the  graphic 
method,  and  seek  to  determine  whether  the  dualistic  form  is  compat- 
ible with  the  theory  of  molecular  unity. 

20.  The  following  symbols  represent  compounds  of  what  class  ? 


H-O-H;   HfOfPOiFerOfEti    2H-(HO);   (P0,)2=0; 
K-0-H-,    Ca-02=ff2-,  C2H5-0-H;2Na-0-H;    C5#902= 


98  BASES,  ACIDS,  AND  SALTS. 

Give  in  each  case  the  name  of  the  compound  so  far  as  you  are  able 
to  infer  it  from  examples  previously  given,  and  show  how  the  sym- 
bol is  related  to  that  of  water. 

21.  Point  out  the  acid  basic  and  neutral  salts  among  the  com- 
pounds represented  by  the  following  symbols  :  —      ^' 


ff,K-02=(C202)    (Hg-0-Hg-0-Hg)-OfS0.2 
Na2=02=CO  K2=02=(C202) 

#2,  Cu=  Of-Si  Cu=02=(N02),  H 

Bi=-0.f(N02\H2       H2,  K~=OfAs  K2=02=(S02-0-S02). 

What  two  classes  of  basic  salts  may  be  distinguished  ?    §  Convert  the 
symbols  into  the  dualistic  form. 

22.  Analyze  reactions  [49  and  50],  and  show  how  far  they  justify 
the  dualistic  form  given  to  the  symbols.     Represent  the  same  reac- 
tions in  the  graphic  form. 

23.  What  class  of  compounds  do  the  following  symbols  represent  ? 

Ag^SfAs        Ag-S-SbS        Ca-S./H^ 

Write  the  symbols  of  the  corresponding  oxygen  compounds. 

24.  Explain  the  theory  of  the  colored  test  papers,  and  the  use  of 
the  terms  acid  and  basic  in  connection  with  them.     To  what  confu- 
sion does  the  double  meaning  of  these  terms  sometimes  lead  ? 

25.  The  members  of  the  series  of  alcohols  stand  in  what  relation 
to  each  other  ?     Does  the  same  relation  exist  between  the  members 
of  the   series  of  fat  acids,  glycols,  &c.  ?     Find  a  general  symbol, 
which  will  represent  the  composition  of  each  of  these  classes  of  com- 
pounds. 

26.  In  what  relations  do  the  alcohols  stand  to  the  fat  acids,  and  the 
glycols  to  the  acids  derived  from  them  ? 

27.  Select  examples  from  each  of  the  classes  of  compounds  de- 
scribed in  sections  40,  41,  and  42,  and  bring  the  symbols  into  com- 
parison with  those  of  some  simple  hydrate  or  anhydride  with  which 
they  exactly  correspond. 

28.  We  are  acquainted  with  a  class  of  compounds  known  as  con- 
densed glycols,  one  of  which  has  the  following  symbol  :  — 

4-  0-  C2H,-  0-  C2H4)  -  OfH2. 


BASES,  ACIDS,   AND  SALTS.  99 

To  what  class  of  salts  does  this  correspond  ? 

29.  Judging  from  the  following  symbols  of  a  few  of  the  salts  of 
tartaric  acid,  what  conclusion  should  you  reach  in  regard  to  the 
atomicity  and  basicity  of  this  acid  ? 


30.  What  is  the   atomicity  and  basicity  of  the   different  acids 
whose  symbols  have  been  given  in  this  chapter  ?     Does  the  basi- 
city of  the  different  hydrocarbon  acids  (§  40  to  §  43)   appear  to 
have  any  connection  with  the  number  of  oxygen  atoms  in  the  rad- 
ical? 

31.  How  do  you  explain  the  state  of  combination  of  the  water 
which  enters  into  the  composition  of  most  crystalline  salts  ?     Show 
by  an  example  how  this  mode  of  combination  is  represented  sym- 
bolically.    What  facts  may  be  adduced  in  support  of  the  opinion 
that  the  molecules  of  water  are  not  a  part  of  the  chemical  type  of 
the  salt. 

NOTE.  —  Should  the  teacher  think  it  best  to  introduce  in  this 
connection  definitions  of  the  several  compounds  formed  after  the 
type  of  ammonia  gas,  he  will  find  them  given  in  sections  166  to  171 
of  Part  II.  ;  and,  if  he  finds  it  necessary,  he  should  dwell  more  at 
length  on  the  acids  and  salts  of  the  type  of  hydrochloric  acid  than 
has  been  thought  necessary  in  this  chapter. 


CHAPTER    X.1 

CHEMICAL    NOMENCLATURE. 

45.  Origin  of  Nomenclature.  —  Previous  to  the  year  1787 
the  names  given  to  chemical  compounds  were  not  conformed  to 
any  general  rules  ;  and  many  of  these  old  names,  such  as  oil  of 
vitriol,  calomel,  corrosive  sublimate,  red  precipitate,  saltpetre, 
sal-soda,  borax,  cream  of  tartar,  Glauber's  and  Epsom  salts,  are 
still  retained  in  ^common  use.  As  chemical  science  advanced, 
and  the  number  of  known  substances  increased,  it  became 
important  to  adopt  a  scientific  nomenclature,  and  the  system 
which  came  into  use  was  due  almost  entirely  to  Lavoisier,  who 
reported  to  the  French  Academy  on  the  subject,  in  behalf  of  a 
committee,  in  the  year  named  above.  In  the  Lavoisierian 
nomenclature  the  name  of  a  substance  was  made  to  indicate  its 
composition  ;  and  at  the  time  of  its  adoption,  and  for  fifty  years 
after,  it  was  probably  the  most  perfect  nomenclature  which 
any  science  ever  enjoyed.  It  was  based,  however,  on  the 
dualistic  theory,  of  which  Lavoisier  was  the  father ;  and,  when 
at  last  the  science  outgrew  this  theory,  the  old  names  lost  much 
of  their  significance  and  appropriateness.  Within  the  last  few 
years  the  English  chemists  have  attempted  to  modify  the  old 
nomenclature  so  as  to  better  adapt  the  names  to  our  modern 
ideas.  Unfortunately  the  result,  like  most  attempts  to  mend  a 
worn-out  garment,  is  far  from  satisfactory,  although  it  is  prob- 
ably the  best  which  under  the  circumstances  could  be  attained. 
The  new  nomenclature  has  not  the  simplicity  or  unity  of  the 
old,  and  its  rules  cannot  be  made  intelligible  until  the  student 
is  more  or  less  acquainted  with  the  modern  chemical  theories. 
Fortunately,  however,  the  admirable  system  of  chemical  sym- 
bols supplies  the  defects  of  the  nomenclature,  and  for  many 

1  In  studying  this  chapter,  the  student  is  expected  to  remember  the  names 
corresponding  to  the  different  symbols,  and  also  the  symbols  corresponding 
to  the  names. 


CHEMICAL,  NO^ENCLATij^fc:  \\1  ^  \  101 

purposes  may  be  used  in  its  place.  We  have,  therefore,  devel- 
oped this  system  first,  but  have  also  used,  meanwhile,  the  corre- 
sponding scientific  narnes<  so  that  the  student  might  become 
familiar  with  the  nomenclature,  and  gather  its  rules  as  he 
advanced.  A  brief  summary  of  these  rules  is  all  that  will  be 
necessary  here. 

46.  Names  of  Elements.  —  The  names  of  the  elements  are 
not  conformed  to  any  fixed  rules.     Those  which  were  known 
before  1787,  such  as  sulphur,  phosphorus,  arsenic,  antimony, 
iron,  gold,  and  the  other  useful  metals,  retain  their  old  names. 
Several  of  the  more  recently  discovered  elements  have  been 
named  in  allusion  to  some  prominent  property  or  some  circum- 
stance connected  with   their   history :    as   oxygen,   from   6£vs 
yewdta  (acid-generator)  ;    hydrogen,   from  vdvp  yewda  (water- 
generator)  ;  chlorine,  from  ^Xopdf  (green)  ;  iodine,  from  lady: 
(violet)  ;  bromine,  from  /fyw/zos  (fetid  odor).     The  names  of  the 
newly  discovered  metals  have  a  common  termination,  urn,  as 
potassium,  sodium,  platinum  ;  and  the  names  of  several  of  the 
newly  discovered   metalloids  end  in  ine,  as  chlorine,  bromine, 
iodine,  fluorine.     Equally  arbitrary  names  have  been  given  to 
the  compound  radicals  ;  but,  with  a  few  exceptions,  they  all 
terminate  in  yl  or  ene,  as  ethyl,  acetyl,  hydroxyl,  and  ethylene, 
acetylene,  &c. 

47.  Names  of  Binary  Compounds!     The  simple  compounds 
of  the  elements  with  oxygen  are  called  oxides,  and  the  specific 
names  of  the  different  oxides  are  formed  by'placing  before  the 
word  "oxide"  the  name  of  the  element,  but  changing  the  termi- 
nation into  ic  or  ous,  to  indicate  different  degrees  of  oxidation, 
and  using  the  Latin  name  of  the  element  in  preference  to  the 
English,  both  for  the  sake  of  euphony  and  in  order  to  secure 
more  general  agreement  among  different  languages.      When 
the  same  element  unites  with  oxygen  in  more  than  two  pro- 
portions, the  Greek  numeral  prefixes,  di,  tri,  tetra,  penta,  &c., 
are  added  to  the  word  "  oxide,"  in  order  to  indicate  the  addi- 
tional degrees.      Formerly  these  compounds  were  called  ox- 
ides of  the  different  elements,  the  degrees  of  oxidation  being 
indicated  solely  by  the  prefixes  ;  and,  as  the  old  names  are  still 
in  very  general  use,  they  are  also  given  in  the  following  ex- 
amples :  — 

1  Compounds  of  two  elements. 


102 


£*  i 

IUM1 

AgO 

NO 
FeO 

New  Names. 

is     Argentic  Oxide 
"     Nitrous  Oxide 
"     Nitric  Oxide 
"     Nitric  Dioxide 
"     Ferrous  Oxide 
.   "     Ferric  Oxide 

or 

u 
u 
u 
u 

a 

NOMENCLATURE. 


Old  Names. 

Oxide  of  Silver 
Protoxide  of  Nitrogen 
Deutoxide  of  Nitrogen 
Peroxide  of  Nitrogen 
Protoxide  of  Iron 
Sesquioxide  of  Iron. 


An  exception  to  the  above  rules  is  sometimes  made  in  the 
case  of  those  oxides  which,  when  combined  with  the  elements 
of  water,  form  acids.  As  has  been  already  stated,  page  85, 
such  compounds  are  called  anhydrides,  but  the  degrees  of  oxi- 
dation are  distinguished  as  before,  thus  :  — 


S03 


C02 


New  Names. 

Sulphurous  Anhydride 
Sulphuric  Anhydride 
Nitrous  Anhydride 
Nitric  Anhydride 
Phosphorous  Anhydride 
Phosphoric  Anhydride 
Carbonic  Anhydride 
Silicic  Anhydride 


Old  Names. 

or  Sulphurous  Acid 

"  Sulphuric  Acid 

"  Nitrous  Acid 

"  Nitric  Acid 

"  Phosphorous  Acid 

"  Phosphoric  Acid 

"  Carbonic  Acid 

"  Silicic  Acid. 


The  names  in  common  use,  even  among  chemists,  of  the 
earths,  the  alkaline  earths,  and  the  alkaline  oxides,  make 
another  important  exception  to  the  general  rules  given  above, 
thus :  — 

AIZ03  Aluminic  Oxide  is  commonly  called     Alumina 

BaO  Baric  Oxide         "  "  "  Baryta 

SrO  Strontic  Oxide    "  "  "  Strontia 

CaO  Calcic  Oxide       "  "  "  Lime 

MgO  Magnesic  Oxide  "  "  "  Magnesia 

KZ0  Potassic  Oxide     "  "  "  Potassa 

NazO  Sodic  Oxide         "  "  "  Soda. 

As  this  last  class  of  oxides  stands  in  the  same  relation  to  the 
bases  in  which  the  previous  class  stands  to  the  acids,  they  have 
also  been  called  by  some  chemists  anhydrides. 

The  names  of  the  binary  compounds  of  the  other  elements 
are  formed  like  those  of  the  oxides. 


CHEMICAL  NOMENCLATIVE. 


103 


Compounds  of  Chlorine       are  called     Chlorides 


"    Bromine        " 

u 

Bromides 

"    Iodine            " 

u 

Iodides 

"    Fluorine        " 

u 

Fluorides 

"    Sulphur         « 
"    Nitrogen       " 
"    Phosphorus    " 
"    Arsenic          " 

u 
M 

M 

Sulphides 

"Nitrides 
PhospluWes 
Arsenides 

"    Antimony      " 
"    Carbon           " 

M 

u 

Antimonides 
CarbomWes. 

Moreover,  the  specific  names  of  the  several  compounds  also 
follow  the  analogy  of  the  oxides,  thus  :  — 

Old  Names. 
Protochloride  of  Tin 
Perchloride  of  Tin 
Subsulphide  of  Iron 
Protosulphide  of  Iron 
Sesquisulphide  of  Iron 
Bisulphide  of  Iron 
Fluoride  of  Calcium. 

Here,  again,  must  be  noticed  several  exceptions  to  the  gen- 
eral rule.  Several  simple  compounds  of  the  elements  with  hy- 
drogen, of  which  the  hydrogen  is  easily  replaced  with  a  metal 
or  positive  radical,  are  called  acids,  and  retain  the  specific 
names  of  the  old  nomenclature,  thus :  — 


New  Names. 

Sn  C/2     is 

Stannous  Chloride 

or 

SnCl      " 

Stannic  Chloride 

a 

Fe^     « 

Diferrous  Sulphide 

u 

FeS       « 

Ferrous  Sulphide 

" 

Fe  S      " 

Ferric  Sulphide 

u 

FeS*     " 

Ferric  Disulphide 

u 

CaFl2    « 

Calcic  Fluoride 

a 

or 


HCl 

HBr  " 

HI  « 

HFl  « 

HnS  " 


Hydric  Chloride  is  called 

Hydric  Bromide  "      " 

Hydric  Iodide  "      " 

Hydric  Fluoride  "      " 

Hydric  Sulphide  "      « 


Hydrochloric  Acid 
Hydrobromic  Acid 
Hydriodic  Acid 
Hydrofluoric  Acid 
Hydrosulphuric  Acid. 


The  last  compound  is  frequently  called  also  sulphuretted 
hydrogen,  and  several  other  hydrogen  compounds  are  named 
after  the  same  analogy,  while  others  again  are  always  called  by 
their  well-known  trivial  names,  thus  :  — 


H3Sb 
H3As 
H,P 


Antimoniuretted  Hydrogen 

Arseniuretted  Hydrogen 

Phospnuretted  Hydrogen 

Ammonia  Gas 

Marsh  Gas  or  Light  Carburetted  Hydrogen 

Olefiant  Gas  or,  as  a  radical,  Ethvlene. 


104  CHEMICAL  NOMENCLATURE. 

48.  Ternary    Compounds.  —  Of  the   old    class   of  ternary 
compounds,  it  is  only  those  which  are  formed  after  the  type  of 
water  for  which  the  rules  of  the  nomenclature  need  at  present 
be  explained. 

49.  Bases.  —  These   we  call  simply  hydrates,  and  for  the 
specific  name  we  take  the  name  of  the  positive  radical,  chang- 
ing the  termination  into  ic  or  ous,  and  using  such  prefixes  as 
circumstances  may  require,  thus  :  — 

New  Names.  Old  Names. 

K-O-H  is   Potassic  Hydrate  or  Hydrate  of  Potassa 

Ca=OfHz  "    Calcic  Hydrate      "    Hydrate  of  Lime 

Fe*OfH9  "    Ferrous  Hydrate    «     j  Hydrate   of  .Protox- 

(      ide  of  Iron. 

Fe*OfH%  «    Ferric  Hydrate      «    j  Hydrate  of  Sesquiox- 

(      ide  of  Iron. 

ZctO^Hi  Zirconic  Hydrate  or  Hydrate  of  Zircoriia. 

50.  Acids.  —  The  inorganic  acids  all  take  their  specific  names 
from  the  name  of  the  most  characteristic  element  of  the  nega- 
tive radical,  which  is  modified  by  terminations  and  prefixes  as 
before,  only  the  last  are  usually  taken   from  the  Greek  rather 
than  the  Latin.     Here  the  old  and  the  new  names  coincide. 

H-0-N02  is  called  Nitric  Acid 

H2=0Z=SOZ  "       "       Sulphuric  Acid 

"       Sulphurous  Acid 


HfOf(S-0-S)      "       "       Hyposulphurous  Acid 

The  specific  names  of  the  organic  acids  are,  as  a  rule,  arbitrary, 
like  tartaric  acid,  citric  acid,  malic  acid,  gallic  acid,  uric  acid, 
and  the  like. 

51.  Salts.  —  The  name  of  a  salt  is  formed  from  the  name 
of  the  acid  from  which  the  salt  is  derived,  preceded  by  the 
names  of  the  basic  radicals.  When  the  name  of  the  acid  ends 
in  ic  the  termination  is  changed  into  ate,  when  in  ous  into  ite. 
Moreover,  the  terminations  ous  and  ic  are  retained  in  connec- 
tion with  the  name  of  the  basic  radical,  and  such  prefixes  are 
used  as  may  be  necessary  for  distinction,  thus  :  — 


Ferric  Sulphate  Pehate  °f 


CHEMICAL  NOMENCLATURE.  105 

New  Names.  Old  Names. 

Ca-OfCO  is  Calcic  Carbonate       or   (Carbonate  of 

(     Lime 

Ca=0,=(S-0-S)  «  Calcic  Hyposulphite   «      Hyposulphite 

(     of  Lime 

Ba=0.2=SO  "  Baric  Sulphite  «       SulPhite  of 

(      Baryta 

Fe-0,=S02  «   Ferrous  Sulphate        «       Protosulphate 

of  Iron 

P 

^),  Mg=Or=PO          "  Ammonio-magnesic  Phosphate 
H,  (NHJ,  Na-=0/PO     "  Hydro-ammonio-sodic  Phosphate. 
H,  NarO^PO  «   Hydro-disodic  Phosphate. 

#4,  Cavi06vi(PC>)2  «    Tetrahydro-calcic  Diphosphate. 

NafOfB405  «   Disodic  Tetraborate  (Borax). 

NOTE.  —  The  rules  of  the  nomenclature  given  above  conform  to 
what  the  author  regards  as  the  best  present  use  among  chemists. 
There  is,  however,  an  important  departure  from  the  more  general 
use,  which  must  not  be  overlooked.  Several  English  authors,  who 
think  that  the  adjectives  derived  from  the  Latin  names  of  the  ele- 
ments, with  terminations  in  ic  and  ous,  are  not  in  harmony  with 
English  idioms,  use  such  terms  as  Gold  Chloride,  Silver  Nitrate,  and 
Iron  Sulphate,  instead  of  Auric  Chloride,  Argentic  Nitrate,  and 
Ferrous  Sulphate.  This  usage,  however,  appears  to  the  writer  open 
to  equally  just  criticism,  besides  abridging  greatly  the  capabilities  of 
the  nomenclature,  which  is  full  of  similar  incongruities.  Nor  does 
he  sympathize  with  the  same  class  of  writers  in  rejecting  the  word 
"  anhydride  "  as  a  part  of  the  name  of  a  substance,  on  the  ground 
that  it  does  not  express  its  constitution,  but  only  a  mode  of  its  deri- 
vation ;  for  a  similar  objection  might  be  urged  with,  equal  force 
against  the  terms  "  acid  "  and  "hydrate."  Moreover,  he  has  thought 
it  best,  in  a  work  designed  chiefly  for  instruction,  not  only  to  intro- 
duce no  novelties,  but  also  to  represent  the  actual  usage,  so  far  as 
possible,  in  all  its  phases.  He  would,  however,  offer  the  following 
suggestions  as  guides  to  the  student  in  selecting  for  his  own  use  a 
more  uniform  and  consistent  system,  hoping  that  before  long  some 
agreement  will  be  reached  among  chemists,  by  which  greater  uni- 
formity may  be  secured.  He  would  recommend,  — 


106  CHEMICAL  NOMENCLATURE. 

First,  that  the  terminations  ic,  ous,  ate,  and  tie,  with  the  modify- 
ing Greek  and  Latin  prefixes,  should  be  used  so  far  as  possible  to 
distinguish  the  quantivalence  of  the  chief  multivalent  radical  of 
the  compound.  Secondly,  that  the  Greek  numeral  prefixes  should 
be  used  when  necessary  to  indicate  the  number  of  atoms  of  any 
radical  which  each  molecule  of  such  compound  contains.  Thirdly, 
that  in  forming  the  name  of  a  compound  it  should  be  the  great 
object  to  indicate  its  composition,  and  that  the  use  of  such  terms  as 
acid,  basic,  or  anhydride  as  parts  of  the  name  should  be  avoided, 
except  when  it  is  desired  to  make  conspicuous  the  peculiar  chemical 
relations  which  they  express. 

By  referring  to  the  list  of  sulphates  on  page  319,  and  to  the  list 
of  sulphites  on  page  315,  the  student  will  find  good  examples  of  the 
application  of  these  principles.  He  will  notice  that  salts  in  which 
the  quantivalence  of  sulphur  is  six  are  called  sulphates,  while  those 
in  which  it  is  four  are  called  sulphites,  and  those  in  which  it  is  two 
hyposulphites  v  Again,  on  page  230  he  will  find  the  proper  applica- 
tion of  the  term  anhydrde  explained,  the  term  acid  and  basic  hav- 
ing been  already  defined  on  page  82. 

Questions  and  Problems. 

1.  Give  the  names  of  the  compounds  represented  by  the  follow- 
ing symbols:  — 

a.  KCl;        K20-,         K2S;        KfOfSO;        K2=02=S02-, 
KfOf(S-O-S); 

b.  FeO-,     Fe=02=ff2;  Fe=02=CO;    Fe=0.fC202;     [Fe2yOs; 
jy0JJ5r6;     [#.2]i0J(JF0,)« 

C.-H-CI-,     H-F-,     H-O-NO^     H-0-NO-,      fffOfSO^ 


2.  Write  the  symbols  of  the  following  compounds  : 

a.  Calcic  Sulphide  ;  Calcic  Sulphite  ;  Calcic  Hyposulphite  ;  Cal- 
cic Sulphate;  Calcic  Hydrate;    Calcic  Sulphohydrate  ;  Calcic  Car- 
bonate ;   Calcic  Sulphocarbonate  ;  Calcic  Silicate. 

b.  Water  ;   Potassic   Hydrate  ;    Nitric  Acid  ;     Potassic  Nitrate  ; 
Nitric  Anhydride  ;  Potassic  Oxide. 

c.  Magnesic    Oxide  ;     Magnesic   Hydrate  ;    Magnesic    Nitrate  ; 
Magnesic    Carbonate  ;    Magnesic  Phosphate  ;    Ammonio-magnesic 
Phosphate. 

N.  B.  Examples  like  the  above  should  be  greatly  multiplied  by 
the  teacher,  pains  being  taken  to  group  together  the  names  and 
symbols  in  the  way  best  calculated  to  exhibit  their  relations  and  to 
assist  the  memory. 


CHAPTER    XI. 

SOLUTION   AND    DIFFUSION. 

52.  Solution.  —  The  solvent  power  of  water  is  one  of  the 
most  familiar  facts  of  common  experience,  and  all  liquids  pos- 
sess the  same  power  to  a  greater  or  less  degree,  but  they  differ 
very  widely  from  each  other  in  the  manifestation  of  their 
solvent  power,  which  for  each  liquid  is  usually  limited  to  a 
certain  class  of  solids.  Thus  mercury  is  the  appropriate  rol- 
vent  of  metals,  alcoliol  of  resins,  ether  of  fats,  and  water  of  salts 
and  of  similar  compounds  of  its  own  type.  Water  is  by  far  the 
most  universal  solvent  known,  and  for  this  reason,  as  well  as 
on  account  of  its  very  wide  diffusion  in  nature,  it  becomes  the 
medium  of  most  chemical  changes.  The  phenomena  of  aqueous 
solution  form  therefore  a  very  important  subject  of  chemical 
inquiry,  and  these  alone  will  be  considered  in  this  connection. 

The  solvent  power  of  water,  even  on  bodies  of  its  own  type, 
differs  very  greatly.  Some  solids,  like  potassic  carbonate,  or 
calcic  chloride,  liquefy  in  the  atmosphere  by  absorbing  the 
moisture  it  contains.  Such  salts  are  said  to  deliquesce,  and  are 
rendered  liquid  by  a  very  small  proportion  of  water.  Other 
salts,  like  calcic  sulphate,  require  for  solution  several  hundred 
times  their  weight  of  water,  and  others  again,  like  baric  sul- 
phate, are  practically  insoluble. 

As  a  general  rule  the  solvent  power  of  water  increases  with 
the  temperature ;  but  here,  again,  we  observe  the  greatest  dif- 
ferences between  different  substances.  While  the  solubility 
of  some  salts  increases  very  rapidly  with  the  temperature,  that 
of  others  increases  not  at  all,  or  only  very  slightly ;  and  there 
are  a  few  which  are  actually  more  soluble  in  cold  water  than 
in  hot.  The  solubility  of  each  substance  is  absolutely  definite 
for  a  given  temperature,  and  we  can  determine  by  experiment 
the  exact  amount  which  100  parts  of  water  will  in  any  case 
dissolve.  The  results  of  such  experiments  are  best  represented 
to  the  eye  by  means  of  a  curve  drawn  as  in  the  accompanying 
figure  on  the  principles  of  analytical  geometry. 


108  SOLUTION  AND  DIFFUSION. 

Fig.  2. 


The  figures  on  the  horizontal  line  indicate  degrees  of  tempera- 
ture, and  those  on  the  vertical  line  parts  of  salt  soluble  in  100 
parts  of  water.  To  find  the  solubility  of  any  salt,  for  a  stated 
temperature,  the  curve  being  given,  we  have  only  to  follow  up 
the  vertical  line  corresponding  to  the  temperature  until  it 
reaches  the  curve,  and  then,  at  the  end  of  the  horizontal  line 
which  intersects  the  curve  at  the  same  point,  we  find  the  num- 
ber of  parts  required.  These  curves  also  show  in  each  case 
the  law  which  the  change  of  solubility  obeys. 

When  a  liquid  has  dissolved  all  of  a  solid  that  it  is  capable  of 
holding  at  the  temperature,  it  is  said  to  be  saturated  ;  but  when 
saturated  with  one  solid  the  liquid  will  still  exert  a  solvent 
power  over  others ;  indeed,  in  some  cases  the  solvent  power  is 
thereby  increased.  When  several  salts  are  dissolved  together 
in  water,  a  definite  amount  of  metathesis  seems  always  to  take 
place,  and  the  different  positive  radicals  are  divided  between 
the  several  acids  in  proportions  which  depend  on  the  relative 
strength  of  their  affinities,  and  on  the  quantities  of  each  pres- 
ent. If  in  this  way  either  an  insoluble  or  a  volatile  product  is 
formed,  the  solid  or  the  gas  at  once  falls  out  of  the  solution, 
and,  the  equilibrium  being  thus  destroyed,  a  new  metathesis 
takes  place,  and  this  goes  on  so  long  as  any  of  these  products 
can  be  formed.  Here,  then,  we  find  a  simple  explanation  of  the 
two  important  laws  already  stated  on  page  37. 


SOLUTION  AND  DIFFUSION.  109 

53.  Solution  of  Gases.  —  Most  liquids,  but  especially  water 
and  alcohol,  exert  on  gases  a  greater  or  less  solvent  power, 
which  is  marked  by  differences  of  manifestation  similar  to 
those  we  have  already  studied  in  the  case  of  solids,  although 
the  peculiar  physical  conditions  of  the  gas  somewhat  modify 
the  result.  Under  the  same  conditions,  the  volume  of  gas  dis- 
solved is  always  the  same ;  but  it  varies  with  the  pressure  of 
the  gas  on  the  surface  of  the  liquid,  with  the  temperature,  and 
with  the  peculiar  nature  of  the  gas  and  the  absorbing  liquid. 
The  quantity1  of  gas  dissolved  by  one  cubic  centimetre  of  a 
liquid  on  which  it  exerts  a  pressure  of  76  c.  m.  is  called  the 
coefficient  of  absorption.  This  coefficient,  in  almost  every  in- 
stance, diminishes  with  the  temperature ;  but,  as  in  the  case  of 
solids,  each  substance  obeys  a  law  of  its  own,  which  must  be 
determined  by  experiment.  The  observed  values  for  se'veral  of 
the  best  known  gases,  when  absorbed  by  water  and  alcohol,  are 
given  in  the  Chemical  Physics,  Table  VII.  With  these  data 
we  can  easily  calculate  the  quantity  of  any  of  these  gases  which 
a  given  volume  of  water  or  alcohol  will  absorb,  assuming  that 
the  gas  exerts  on  the  liquid  a  pressure  of  76  c.  m.  Moreover, 
since  the  quantity  of  a  gas  absorbed  by  a  liquid  varies  directly 
as  the  pressure  which  the  gas  exerts  upon  it,  we  can  easily 
calculate  from  the  first  result  the  quantity  absorbed  at  any 
given  pressure.  Again,  it  is  a  direct  consequence  of  the  last' 
principle  that  at  a  fixed  temperature  a  given  mass  of  liquid  will 
dissolve  the  same  volume  of  gas,  whatever  may  be  the  pressure. 
Lastly,  if  a  mass  of  liquid  is  exposed  to  an  atmosphere  of 
mixed  gases,  it  will  absorb  of  each  the  same  quantity  as  if  this 
gas  was  alone  present  and  exerting  on  the  liquid  the  same 
partial  pressure  which  falls  to  its  share  in  the  atmosphere. 
The  amount  dissolved  of  each  gas  is  easily  calculated  when  the 
partial  pressure  and  the  coefficient  of  absorption  are  known. 
It  is  thus  that  water  absorbs  the  oxygen  and  nitrogen  gases  of 
our  terrestrial  atmosphere ;  and  the  fact  that  these  two  gases 
are  found  dissolved  in  the  ocean  in  very  different  proportions 
from  those  present  in  the  atmosphere  is  a  conclusive  proof  that 
the  air  is  a  mixture,  and  not,  as  was  formerly  supposed,  a  chem- 
ical compound. 

1  By  quantity  of  gas  is  here  meant  the  volume  in  cubic  centimetres  meas- 
ured under  the  standard  conditions  of  temperature  and  pressure. 


110  SOLUTION  AND  DIFFUSION. 

54.  Solution  and  Chemical  Change.  —  There  seems  at  first 
sight  to  be  a  wide  difference  between   solution  and  chemical 
change ;  for,  while  in  the  first  the  solid  body  becomes  diffused 
through   the   liquid   menstruum   without   losing    its    chemical 
identity  or  destroying  that  of  the  liquid,  there  is  in  the  second 
a  complete  identification  of  the  combining  substances  in  the 
resulting  compound. 

The  same  wide  difference  appears  also  between  mechanical 
and  chemical  solution,  which  are  sometimes  confounded  by 
students,  because,  unfortunately,  the  same  term  has  been  applied 
to  both.  When  salt  or  sugar  is  dissolved  in  water,  the 
differences  between  salt  and  solvent  are  preserved  ;  but  when 
chalk  is  dissolved  in  hydrochloric  acid,  or  copper  in  nitric  acid, 
there  is^  a  complete  identification  of  the  differences  in  the 
resulting  compound;  and  the  only  ground  for  calling  such 
chemical  changes  solution  is  the  fact  that  the  solution  of  the 
resulting  salt  in  the  water,  used  as  the  medium  of  the  chemical 
change,  is  frequently  an  essential  condition  of  the  process. 

But  if,  instead  of  comparing  extreme  cases,  we  study  the 
whole  range  of  chemical  phenomena,  we  shall  find  that  the 
distinction  is  by  no  means  so  clearly  marked.  In  many  cases 
what  seems  to  be  a  simple  solution  can  be  shown  to  be  a  mixed 
effect  at  least  of  solution  and  chemical  combination ;  and  be- 
tween this  condition  of  things,  where  the  evidence  of  chemical 
combination  is  unmistakable,  and  a  simple  solution,  like  that  of 
sugar  in  water,  we  have  every  degree  of  gradation.  To  such 
an  extent  is  this  true,  that  the  facts  seem  to  justify  the  opinion 
that  solution  is  in  every  case  a  chemical  combination  of  the 
substances  dissolved  with  the  solvent,  and  that  it  differs  from 
other  examples  of  chemical  change  only  in  the  weakness  of  the 
combining  force. 

The  metallic  alloys  afford  another  striking  illustration  of  the 
same  principle.  They  are  originally  solutions  of  one  metal  in 
another ;  but  in  many  cases  the  result  is  greatly  modified  by 
the  chemical  affinities  of  the  metals  and  their  tendency  to  form 
definite^  chemical  compounds. 

55.  Liquid  Diffusion.  —  Closely  connected  with  the  phe- 
nomena of  solution  are  those  of  liquid  diffusion.     These  phe- 
nomena may  be  studied  in  their  simplest  form,  by  placing  an 
open  vial  filled  with  a  solution  of  some  salt  in  a  much  larger 


SOLUTION  AND  DIFFUSION.  Ill 

jar  of  pure  water,  as  shown  in  Fig.  3,  and  so  carefully  arranging 
the  details  of  the  experiment  that  the  surfaces  of  the  two 
liquids  may  be  brought  in  contact  without  mixing  them  me- 
chanically.    It  will  then  be  found  that  the  salt  molecules  will 
slowly  escape  from  the  vial  and  spread 
throughout   the    whole   volume    of  the 
water.     The  rate   of   the    diffusion    in- 
creases  with    the    temperature    equally 
for  all   substances,  and   the  whole  phe- 
nomenon   is    probably    caused   by    that 
same    molecular    motion    to    which    we 
refer  the  effects  of  heat.     At  best,  how- 
ever, the  diffusion  is  very  slow,  as  we 
should   expect,  considering   the   limited 
freedom    of    motion    which    the    liquid 
molecules  possess.     It  is  found,  also,  that 
the  rate  of  diffusion  differs  very  greatly 

for  the  different  soluble  salts  ;  but  these  may  be  divided  into 
groups  of  equidiffusive  substances,  and  the  rates  of  diffusion  of 
the  several  groups  bear  to  each  other  simple  numerical  ratios. 
If  a  mixture  of  salts  be  placed  in  the  vial,  it  is  found  that  the 
presence  of  one  salt  affects  to  some  degree  the  diffusion  of  the 
other ;  but  if  the  difference  of  rate  is  considerable,  a  partial 
separation  may  be  effected,  and  even  weak  chemical  compounds 
may  be  thus  decomposed. 

56.  Crystalloids  and  Colloids.  —  There  is  a  very  great  differ- 
ence of  diffusive  power  between  the  ordinary  crystalline  salts 
(including  most  of  the  common  acids  and  bases)  and  such  sub- 
stances as  gum,  caramel,  gelatine,  and  albumen,  which  are 
incapable  of  crystallizing,  and  which  give  insipid  viscid  solu- 
tions, readily  forming  into  jelly  ;  hence  the  name  colloids,  from 
KoXXrj,  glue.  The  last  class  is  distinguished  by  a  remarkable 
sluggishness  and  indisposition  to  diffusion ;  as  is  illustrated  by 
the  fact  that  sugar,  one  of  the  least  diffusible  of  the  crystalloids, 
diffuses  seven  times  more  rapidly  than  albumen,  and  fourteen 
times  more  rapidly  than  caramel.  Our  theories  would  lead  us 
to  believe  that  this  great  difference  of  diffusive  power  is  caused 
by  the  fact  that  the  molecules  of  colloids  are  far  more  complex 
atomic  aggregates  than  those  of  crystalloids,  and  therefore  are 
heavier  and  move  more  slowly.  Moreover,  the  diffusive  power 


112  SOLUTION  AND  DIFFUSION. 

is  only  one  of  many  characters  which  point  to  a  great  molecu- 
lar difference  between  these  two  classes  of  substances. 

57.  Dialysis.  —  The  difference  of  diffusive  power  between 
the  two  classes  of  compounds  distinguished  in  the  last  section 
is  still  further  increased  when  the  aqueous  solution  is  separated 
from  the  pure  water  by  some  colloidal  membrane,  and  upon  this 
fact  Professor  Graham  of  London,  to  whom  we  owe  our  whole 
knowledge  of  this  subject,  has  based  a  simple  method  of  sepa- 
rating crystalloids  from  colloids,  which  he  calls  dialysis. 

A  shallow  tray  is  prepared  by  stretching  parchment  paper 
(which  is  itself  an  insoluble  colloid)  over  one  side  of  a  gutta- 
percha  hoop,  and  holding  it  in  place  by  a  somewhat  larger  hoop 
of  the  same  material.  The  solution  to  be  dialysed  is  poured  into 
this  tray,  which  is  then  floated  on  pure  water  whose  volume 
should  be  eight  or  ten  times  greater  than  that  of  the  solution. 
Under  these  conditions  the  crystalloids  will  diffuse  through  the 
porous  septum  into  the  water,  leaving  the  colloids  on  the  tray, 
and  in  the  course  of  two  or  three  days  a  more  or  less  complete 
separation  of  these  two  classes  of  substances  will  have  taken 
place. 

In  this  way  arsenious  acids  and  similar  crystalloids  may  be 
separated  from  the  colloidal  materials,  with  which,  in  cases  of 
poisoning,  they  are  frequently  found  mixed  in  the  stomach  ;  and 
by  an  application  of  the  same  method  alumina,  ferric  oxide, 
chromic  oxide,  stannic,  metastannic,  titanic,  molybdic,  tungstic, 
and  silicic  acids  have  all  been  obtained  dissolved  in  water  in  a 
colloidal  condition.  All  these  substances  usually  exist  in  a 
crystalline  condition.  The  colloidal  condition  appears  to  be  an 
abnormal  state,  and  in  almost  all  such  substances  there  is  a 
tendency  towards  the  crystalloid  form. 

58.  Diffusion  of  Gases.  —  Gases  diffuse  much  more  rapidly 
than  liquids,  as  we  should  naturally  expect  from  the  greater 
freedom  of  motion  which  their  molecules  possess.     Moreover, 
if  the  theory  of  the  molecular  condition  of  gases  is  correct,  we 
ought  to  be  able  to  calculate  the  relative  rates  of  diffusion  of 
different  gases  from  their  respective  molecular  weights.     If  it 
is  true,  as  stated  on  page  13,  that  at  any  given  temperature 

%m  V^  —  ^m'  V* 
then  it  follows  that 

V\  V  =  \J$m' :  v/£  m  =  y/Sp.  Gr'. :  y/Sp.  Gr. 


I 
SOLUTION  AND  DIFFUSION.  113 

Hence,  if  two  masses  of  gas  are  in  contact,  the  molecules  of 
either  gas  must  move  into  the  space  filled  by  the  other  with 
velocities  which  are  inversely  proportional  to  the  square  roots 
of  the  respective  specific  gravities.  If  one  gas  is  hydrogen  ( Sp. 
Gr.  =  1),  and  the  other  oxygen  (Sp.  Gr.  —  16),  the  molecules 
of  hydrogen  must  move  past  the  section  separating  the  two 
masses  four  times  as  rapidly  as  those  of  oxygen ;  and,  since  all 
gas  molecules  occupy  the  same  volume,  it  follows  further  that 
four  volumes  of  hydrogen  must  enter  the  space  filled  by  the 
oxygen,  while  one  volume  of  oxygen  is  passing  in  the  opposite 
direction  Numerous  experiments  have  fully  confirmed  this 
theoretical  deduction,  and  the  close  agreement  between  theory 
and  experiment  furnishes  important  evidence  in  favor  of  the 
theory  itself.  Such  experiments  can  be  made,  moreover,  with 
great  accuracy,  since  the  molecular  motion  is  not  arrested 
by  various  porous  septa,  which  may  be  used  to  separate  the 
two  masses  of  gas,  and  which  entirely  prevent  the  passage  of 
gas  currents  that  might  otherwise  vitiate  the  results. 


CHAPTER  XII. 

RELATION  OF  THE  ATOMS  TO  HEAT. 

59.  The  Atmosphere.  —  The  earth  is  surrounded  by  an  ocean 
of  aeriform  matter  called  the  atmosphere,  and  many  of  the  most 
important  chemical  changes  which  we  witness  in  nature  are 
caused  by  the  reaction  of  this  atmosphere  on  the  substances 
which  it  surrounds  and  bathes.     The  great  mass  of  the  atmos- 
phere consists  of  the  two  elementary  gases,  oxygen  and  nitro- 
gen, mixed  together  in  the  proportions  indicated  in  the  follow- 
ing table :  — 

Air  Composition  Composition 

contains.  By  Volume.  By  Weight. 

Oxygen,  20.96  23.185 

Nitrogen,  79.04  76.815 

100.  100. 

That  the  air  is  a  mixture,  and  not  a  chemical  compound,  is 
proved  by  the  action  of  solvents  upon  it  (§  53)  ;  but,  neverthe- 
less, the  analyses  of  air  collected  in  different  countries,  and  at 
different  heights  in  the  atmosphere,  show  a  remarkable  con- 
stancy in  its  composition.  Besides  these  two  gases,  which  make 
up  over  93  per  cent  of  its  whole  mass,  the  air  always  contains 
variable  quantities  of  aqueous  vapor,  carbonic  anhydride,  and 
ammonia,  and  sometimes  also  traces  of  various  other  gases  and 
vapors. 

60.  Burning.  —  Of  the  two  chief  constituents  of  the  atmos- 
phere, nitrogen  gas  is  a  very  inert  substance,  and  serves  chiefly 
to  restrain  its  more  energetic  associate.     Oxygen  gas,  on  the 
other  hand,  is  endowed  with  highly  active  affinities,  and  tends 
to  enter  into  combination  with  other  elementary  substances, 
and  with  many  compounds  which  are  not  already  saturated 
with  this  all-pervading  element.     Many  of  these  substances, 
such  as  phosphorus,  sulphur,  petroleum,  coal,  and  wood,  have 
such  a  strong  affinity  for  oxygen,  that,  under  certain  conditions, 
they  will  absorb  it  from  the  atmosphere,  and  combine  with  it 


COMBUSTION.  115 

under  the  evolution  of  heat  and  light.  These  substances  are 
said  to  be  combustible,  and  the  process  of  combination  is  called 
combustion.  Moreover,  all  burning  with  which  we  are  familiar 
in  common  life  consists  in  the  union  of  the  burning  body  with 
the  oxygen  of  the  air.  The  chemical  process  in  these  cases 
may  be  expressed,  like  any  other  chemical  reaction,  in  the  form 
of  an  equation. 

Burning  of  Hydrogen  Gas. 

Hydrogen  Gas.  Aqueous  Vapor. 

2  HHS  -f  ©-©  =  2  HL®. 

I  •* 


Burning  of  Carbon  {Charcoal'). 

Carbon.  Carbonic  Anhydride. 

C  +  ©=©  =  @©2.  [54] 


Burning  of  Benzole. 

Benzole. 

15®=©  =  12@©2  +  6SI2©.         [55] 


Burning  of  Alcohol. 

Alcohol. 

3©-©  =  2@©2  +  3H32®.  [56] 


Burning  of  Sulphur. 

Sulphurous  Anhydride. 

2©=©  =  2^©2.  [57] 


Burning  of  Phosphorus. 

Phosphoric  Anhydride. 

+  5©=©  =  2P,O«.  [58] 


Burning  of  Magnesium. 

Magnesic  Oxide. 

2  Mg  +  ©=©  —  2  MgO.  [59] 

The  four  substances,  hydrogen  gas,  charcoal,  benzole,  and 
alcohol,  may  be  regarded  as  types  of  our  ordinary  combustibles  ; 
and,  as  the  first  four  reactions  show,  the  products  of  their  com- 
bustion are  aeriform.  Moreover,  these  products  are  wholly 
devoid  of  any  sensible  qualities,  and  hence  the  apparent  annihi- 


116  COMBUSTION. 

lation  of  the  burning  substance,  and  the  reason  that  for  so  long 
a  period  the  nature  of  the  process  remained  undiscovered.  That 
these  qualities  of  the  products  of  ordinary  combustion  are  not  ne- 
cessary conditions  of  the  process,  but  remarkable  adaptations  in 
the  properties  of  those  combustibles  which  are  our  artificial 
sources  of  light  and  heat,  is  shown  by  the  fact,  that,  in  the  last 
two  reactions,  the  products  of  the  combustion  are  solids,  while 
in  [57]  the  product  is  a  noxious  suffocating  gas. 

A  careful  inspection  of  the  reactions  will  also  teach  the 
student  several  other  important  facts  in  regard  to  the  processes 
here  represented.  It  will  be  seen  that,  in  the  burning  of 
hydrogen  gas,  two  volumes  of  hydrogen  gas  and  one  volume 
of  oxygen  gas  combine  to  form  two  volumes  of  aqueous  vapor. 
It  will  further  be  noticed,  that,  in  the  burning  of  carbon  and  of 
sulphur,  a  given  volume  of  oxygen  gas  yields  in  each  case  its 
own  volume  of  the  aeriform  product.  The  carbon  in  the  one 
case,  and  the  sulphur  in  the  other,  are  absorbed,  as  it  were,  by 
the  gas,  without  any  increase  of  volume.  Further,  if  the  ex- 
periments are  made,  which  these  reactions  represent,  it  will 
appear  that,  in  all  those  cases  where  the  combustible  is  repre- 
sented as  a  gas,  the  combustion  is  accompanied  by  flame,  while 
in  the  case  of  carbon,  which  is  a  fixed  solid,  there  is  no  proper 
flame.  Hence  we  learn  that  flame  is  burning  gas,  and  that 
only  those  substances  burn  with  flame. which  are  either  gases 
themselves,  or  which,  at  a  high  temperature,  become  vola- 
tilized, or  generate  combustible  vapors.  Still  other  important 
facts  connected  with  the  process  of  combustion  will  be  learned 
by  solving  the  following  problems  according  to  the  rules  al- 
ready given  (§§  24  and  25). 

Problem.  How  many  cubic  centimetres  of  hydrogen  gas, 
and  how  many  of  oxygen  gas,  are  required  to  form  one  cubic 
centimetre  of  liquid  water?1  Ans.  1,240cm8  of  hydrogen 
gas,  and  620  ~(Tm  of  oxygen  gas. 

Problem.  How  many  cubic  metres  of  air  are  required  to 
burn  448  kilogrammes  of  coal,  assuming  that  the  coal  is  pure 
carbon  ?  Ans.  833.333  m8  of  oxygen  gas,  or  3,975.83  m8  of 
atmospheric  air. 

1  Here,  as  in  all  other  problems  throughout  the  book,  it  is  understood,  unless 
otherwise  expressly  stated,  that  the  measurements  and  weights  are  all  taken  at 
the  standard  temperature  and  pressure.  (Compare  §§  10  and  13.) 


COMBUSTION.  117 

Problem.  How  many  cubic  metres  of  carbonic  anhydride 
are  formed  by  the  burning  of  1,000  kilogrammes  of  coal,  as- 
suming, as  before,  that  the  coal  is  pure  carbon  ?  Ans.  1,860. 

Problem.  How  many  litres  of  carbonic  anhydride,  and 
how  many  of  aqueous  vapor,  would  be  formed  by  burning  one 
litre  of  benzole  vapor  ?  Ans.  Simple  inspection  of  the  equa- 
tion shows  that  6  litres  of  the  first  and  3  litres  of  the  second 
would  be  formed. 

Problem.  How  many  litres  of  carbonic  anhydride,  and  how 
many  of  aqueous  vapor,  would  be  formed  by  burning  one  litre 
of  liquid  alcohol  (C2tf60)  ?  Sp.  Gr.  of  liquid  at  0°  =  0.815. 
Ans.  One  litre  of  alcohol  weighs  815  grammes  or  9,097  criths, 
and,  since  the  Sp.  Gr.  of  alcohol  vapor  is  23,  this  quantity  of 
liquid  would  yield  395.6  litres  of  vapor.  Hence  there  would 
be  formed  2  X  395.6  =  791,2  litres  of  carbonic  anhydride,  and 
3  X  395.6=  1,186.8  litres  of  aqueous  vapor. 

61.  Heat  of  Combustion.  —  The  reactions  of  the  last  section 
represent  only  the  chemical  changes  in  the  processes  of  burning. 
The  physical  effects  which  accompany  the  chemical  changes 
our  equations  do  not  indicate,  but  it  is  these  remarkable  mani- 
festations of  power  which  chiefly  arrest  the  student's  attention, 
and  on  this  power  the  importance  of  the  processes  of  combus- 
tion as  sources  of  heat  and  light  wholly  depends. 

The  immediate  cause  of  the  power  developed  in  the  process 
of  combustion  is  to  be  found  in  the  clashing  of  material  atoms. 
Urged  by  that  immensely  powerful  attractive  force  we  call 
chemical  affinity,  the  molecules  of  oxygen  in  the  surrounding 
atmosphere  rush,  from  all  directions,  and  with  an  incalculable 
velocity,  upon  the  burning  body.  The  molecules  of  oxygen 
thus  acquire  an  enormous  moving  power ;  and  when,  at  the 
moment  of  chemical  union,  the  onward  motion  is  arrested, 
this  moving  power  is  distributed  among  the  surrounding  mole- 
cules, and  is  manifested  in  the  phenomena  of  heat  and  light.1 
(Compare  §  12.) 

1  According  to  our  best  knowledge,  the  phenomena  of  light  are  merely 
another  manifestation  of  the  same  molecular  motion  which  causes  the  phe- 
nomena of  heat.  When  we  speak  of  the  amount  of  heat  produced,  we  refer 
always  to  the  total  amount  of  molecular  motion;  although,  even  in  the  most 
brilliant  illumination,  the  amount  of  mechanical  power  manifested  as  light 
appears  to  be  inconsiderable  as  compared  with  that  which  takes  the  form  of 
heat. 


118  COMBUSTION. 

The  quantity  of  heat  evolved  during  combustion  varies 
very  greatly  with  the  nature  of  the  combustible  employed,  but 
it  is  always  constant  for  the  same  combustible  if  burnt  under 
the  same  conditions,  and  is  exactly  proportional  to  the  weight 
of  combustible  consumed.  We  give  in  the  following  table  the 
amount  of  heat  evolved  by  one  kilogramme  of  several  of  the 
most  common  combustibles  when  they  are  burnt  in  oxygen 
gas  in  their  ordinary  physical  state.  The  numbers  represent 
what  is  called  the  calorific  power  of  the  combustible.  With 
the  exception  of  the  two  last,  which  are  only  approximate 
values,  they  are  the  results  of  very  accurate  experiments 
made  by  Favre  and  Silbermann. 

Calorific  Power  of  CombustibUs. 

Units.  Units. 

Hydrogen,  34,462  Sulphur,  2,221 

Marsh  Gas,  ,        13,063  Wood  Charcoal,  8,080 

defiant  Gas,  11,858  Carbonic  Oxide,  2,400 

Ether,  9,027  Dry  Wood       (about),  3,654 

Alcohol,  7,184  Bituminous  Coal,  "  7,500 

The  calorific  power  of  our  ordinary  hydrocarbon  fuels  may 
be  calculated  approximately  when  their  composition  is  known. 
Most  of  these  combustibles  contain  more  or  less  oxygen,  and 
it  is  found,  as  might  be  expected,  that  the  amount  of  heat 
developed  by  the  perfect  combustion  of  the  fuel  is  equal 
to  that  which  would  be  produced  by  the  perfect  combus- 
tion of  all  the  carbon,  and  of  so  much  of  the  hydrogen  as 
is  in  excess  of  that  required  to  form  water  with  the  oxygen 
present.  The  rest  of  the  hydrogen  may  be  regarded,  so  far 
as  relates  to  the  present  problem,  as  in  combination  with  oxy- 
gen in  the  state  of  water ;  and  in  estimating  the  available  heat 
produced,  we  must  deduct  the  amount  of  heat  required  to  con- 
vert, not  only  this  water  into  steam,  but  also  any  hygroscopic 
water  which  may  be  present.  Moreover,  if  we  use  in  our  cal- 
culation the  value  of  the  calorific  power  of  hydrogen  given  in 
the  table  above,  we  must  also  deduct  the  amount  of  heat  re- 
quired to  convert  into  vapor  all  the  water  formed  in  the  process 
of  burning,  because,  in  the  experiments  by  which  this  value 
was  obtained,  the  aqueous  vapor  formed  was  subsequently  con- 
densed to  water  and  gave  out  its  latent  heat. 

Problem.  Given  the  average  composition  of  air-dried  wood 
as  in  the  table,  to  find  the  calorific  power. 


Carbon,  400 

Hydrogen,  48 

Oxygen,  328 

Nitrogen  and  Ash,       24 
Hygroscopic  Water,  200 
1000 


COMBUSTION.  119 

From   the   results  of  analysis   we   easily 

deduce 

Quantity  of  H  in  combination  with  0      41 
"  "     available  as  fuel  7 

Quantity  of  water  formed  by  burn- 

ing  48  parts  hydrogen 
Hygroscopic  Water  200 

Total  quantity  of  water  evaporated     632 

Units  of  Heat. 

400  grammes  of  carbon  yield 3,232 

7         "         "    hydrogen  " 241 

^473 

Deduct  amount  of  heat  required  to  convert  632  grammes  pf 

water  into  vapor.     (See  §  14.) 339 

Calorific  power  of  air-dried  wood 3,134 

From  the  mechanical  equivalent  of  heat  given  on  page  14, 
and  from  the  data  of  the  above  table,  we  can  easily  calculate 
the  mechanical  power  developed  in  ordinary  combustion,  and 
the  student  will  be  surprised  to  find  how  great  this  power  is. 
The  burning  of  one  kilogramme  of  charcoal  produces  an 
amount  of  heat  which  is  equivalent  to  8,080  X  423  =  3,41 7,840 
kilogramme  metres  ;  that  is,  the  moving  power  which  is  de- 
veloped by  the  clashing  of  the  atoms  during  the  combustion 
of  this  small  amount  of  coal  is  equal  to  that  which  would  be 
produced  by  the  fall  of  a  mass  of  rock  weighing  8,080  kilo- 
grammes over  a  precipice  423  metres  high,  and,  could  this 
power  be  all  utilized,  it  would  be  adequate  to  raise  the  same 
weight  to  the  same  height,  or  to  do  any  other  equivalent 
amount  of  work.  The  steam-engine  is  a  machine  for  apply- 
ing this  very  power  to  produce  mechanical  results ;  but,  unfor- 
tunately, in  the  best  engines  we  do  not  utilize  much  more  than 
2\j  of  the  power  of  the  fuel ;  and  to  find  a  more  economical 
means  of  converting  heat  into  mechanical  effect  is  one  of  the 
great  problems  of  the  present  a?e. 

62.  Calorific  Intensity.  —  The  calorific  intensity  of  fuel  is  to 
be  carefully  distinguished  from  its  calorific  power.  By  calorific 
power  is  meant,  as  we  have  seen,  the  total  quantity  of  heat 
developed  by  the  combustion  of  a  given  amount  of  fuel.  By 
calorific  intensify,  we  mean  the  maximum  temperature  de- 
veloped in  the  process  of  combustion.  Provided  the  products 
are  the  same,  the  total  amount  of  heat  produced  in  any  case  is 


120  COMBUSTION. 

not  materially  influenced  by  the  rapidity  of  the  process  ;  but 
it  is  evident  that  the  temperature  pf  the  burning  fuel  will  de- 
pend, other  things  being  equal,  on  the  rapidity  with  which  the 
heat  is  developed  as  compared  with  the  rapidity  with  which  it 
is  dissipated  through  surrounding  objects  ;  and,  when  the  com- 
bination with  oxygen  is  very  slow,  the  heat  may  be  dissipated 
as  fast  as  it  is  generated,  and  then  the  temperature  of  the 
burning  body  will  not  rise  above  that  of  the  surrounding  at- 
mosphere, as  is  the  case  in  many  of  the  processes  of  slow  com- 
bustion. 

Assuming,  however,  that  all  the  heat  is  retained  by  the 
products  of  combustion,  we  can  calculate  the  maximum  tem- 
perature which  can  in  any  case  be  produced,  provided  the 
calorific  power  of  the  fuel  and  the  specific  heat  of  the  products 
of  combustion  are  known.  The  calorific  intensity  is  simply 
the  temperature  to  which  the  heat  generated  by  the  burning 
of  each  portion  of  the  fuel  can  raise  the  products  of  its  own 
combustion.  Assume  that  the  quantity  burnt  is  one  kilo- 
gramme, that  the  calorific  power  or  number  of  units  of  heat 
produced  is  (7,  that  the  weights  of  the  various  products  of  com- 
bustion are  W,  W,  W",  &c.,  and  that  the  specific  heats  of 
these  products  are  S,  &,  S",  &c.  Then  WS  +  W'S'  +  W"S" 
-|-&c.,  represents  the  amount  of  heat  required  to  raise  the  tem- 
perature of  the  whole  mass  of  the  products  one  centigrade  de- 
gree (§  16),  —  and  the  maximum  temperature,  to  which  these 
products  can  be  raised  in  the  process  of  combustion,  must  be 


- 


Problem.  Find  the  calorific'  intensity  of  charcoal  burnt  in  pure 
oxygen,  and  also  in  air  under  constant  atmospheric  pressure. 

Solution.  By  [54]  we  easily  find  that  each  kilogramme  of 
carbon  yields,  by  burning,  3.67  kilogrammes  of  carbonic  anhy- 
dride, which  is  the  sole  product  of  its  combustion  when  burnt 
in  pure  oxygen.  The  specific  heat  of  carbonic  anhydride 
(Chem.  Phys.  235)  is  0.2164.  The  calorific  power  of  charcoal 
is  8,080.  By  substituting  these  values  in  [60]  we  get  T  = 
10,174°. 

When  the  charcoal  burns  in  air,  the  3.67  kilogrammes  of 
carbonic  anhydride  formed  by  the  combustion  are  mixed  with  a 


COMBUSTION.  121 

large  mass  of  inert  nitrogen,  which  must  bo  regarded  as  one  of 
the  products  of  the  combustion.  The  weight  of  this  nitrogen  is 
easily  calculated  from  the  known  composition  of  air  by  weight 
(§  59)  and  from  the  amount  of  oxygen  consumed  in  the  process. 

23.2  :  76.8  =  2.67  :  x ;  or  x  =  2.67  X  3.31  =  8.84. 

We  have  now,  besides  the  values  given  above,  W  =  8.84 
and  S,'  the  specific  heat  of  nitrogen,  equal  to  0.244.  Whence 

T  —  2,738°. 

Problem.  Find  the  calorific  intensity  of  hydrogen  gas  burnt 
in  oxygen  and  burnt  in  air. 

Solution.  One  kilogramme  of  hydrogen  yields  9  kilogrammes 
of  aqueous  vapor.  The  specific  heat  of  aqueous  vapor  is  0.4805. 
The  calorific  power  of  hydrogen  is  not  so  great  when  the  gas 
is  burnt  under  ordinary  conditions  as  that  given  in  the  table  on 
page  118  ;  for  in  the  experiments  of  Favre  and  Silbermann  the 
vapor  formed  by  the  combustion  was  subsequently  condensed 
to  water,  and  gave  out  its  latent  heat,  while  in  a  burning  flame 
of  hydrogen  no  such  condensation  takes  place.  Hence  C  = 
34,462  —  (537  X  9)  —  29,629.  We  also  have  W=  9  and 
S=  0.  480.  Whence  T=  6,853°. 

When  hydrogen  is  burnt  in  air,  the  nitrogen,  mixed  with  the 
aqueous  vapor,  weighs  26.49  kilogrammes  and  S1  is  the  same 
as  in  the  previous  problem.  Whence  T  =  2,746°. 

It  appears  then  from  these  problems,  that,  although  the 
calorific  power  of  hydrogen  is  much  greater  than  that  of  car- 
bon, its  calorific  intensity  is  less.  But  it  must  be  remembered 
that  the  conditions  assumed  in  these  problems  are  never  real- 
ized in  practice,  for  the  heat  generated  by  the  combustion  is 
never  wholly  retained .  in  the  products.  The  process  of  com- 
bustion requires  a  certain  time,  and  during  this  time  a  portion 
of  the  heat  escapes.  Moreover,  more  air  passes  through  the 
combustible  than  is  required  for  perfect  combustion,  and  many 
of  the  data  which  enter  into  the  calculation  are  uncertain. 
The  results,  therefore,  can  only  be  regarded  as  approximate. 
The  theoretical  conditions  are  most  nearly  realized  in  a  gas 
flame,  and  especially  in  that  form  of  burner  known  as  the 
Bunsen  lamp.  The  temperature  of  the  flame  of  this  lamp, 
when  carefully  regulated,  is  very  nearly  that  which  the  theory 
would  assign. 


122  COMBUSTION. 

63.  Point  of  Ignition.  —  In  order  that  a  combustible  body 
should  take  fire,  and  continue  burning  in  the  atmosphere,  it 
must  be  heated  to  a  certain  temperature,  and  maintained  at 
this  temperature.     This  temperature  is  called  the  point  of  igni- 
tion ;  and  although  it  cannot  always  be  accurately  measured, 
and  is  undoubtedly  more  or  less  variable  under  different  con- 
ditions, yet,  nevertheless,  it  is  tolerably  constant  for  each  sub- 
stance.    For  different  substances  it  differs  very  greatly.    Thus 
phosphorus  takes  fire  below  the  boiling  point  of  water,  sulphur 
at  260°,  wood  at  a  low  red  heat,  anthracite  coal  only  at  a  full 
red  heat,   while  iron  requires  the   highest  temperature  of  a 
forge.     If  a  burning  body  is  cooled  below  its  point  of  ignition, 
it  goes  out;  and  our  ordinary  combustibles   continue  burning 
in  the  air  only  because  the  heat  evolved  by  the  burning  main- 
tains the  temperature  above  the  required  point.     If  the  tem- 
perature of  the  combustible  is  not  maintained  sufficiently  high, 
either  because  the  chemical  union  is  too  slow,  or  because  the 
calorific  power  is  too  small,  then  the  combustible  will  not  con- 
tinue to  burn  in  the  air  of  itself,  although  it  may  burn  most 
readily   if  its    temperature    is    sustained    by  artificial   means. 
Hence  many  of  the  metals  which  will  not  burn  in   the   air 
burn  readily  in  the  flame  of  a  blowpipe,  and  an  iron  watch- 
spring  burns  like  a  match  in  an  atmosphere  of  pure  oxygen. 
The  calorific  intensity  of  all  combustibles,  when  burnt  in  the 
atmosphere,  is,  as  we  have  seen,  greatly  reduced  by  the  pres- 
ence of  nitrogen  ;  and  hence  it  is  that,  although  the  burning 
watch-spring  is  maintained  above  the  point  of  ignition  in  pure 
oxygen,  it  soon  falls  below   this    temperature,  and  goes  out 
when  ignited  in  the  air.     Thus  it  is  that  the  nitrogen  of  our 
atmosphere  exerts  a  most  important  influence  on  the  action  of 
the  fire  element ;  and  it  can  easily  be  seen  that,  were  it  'not  for 
these  provisions  in  the  constitution  of  nature,  by  which  the 
active  energies  of  oxygen  are  kept  within  certain  limits,  no 
combustible  material  could  exist  on  the  surface  of  the  earth. 

64.  Calorific  Power  derived  from  the  Sun.  —  The  great  mass 
of  the  crust  of  our  globe  consists  of  saturated  oxygen  com- 
pounds, or,  in  other  words,  of  burnt  materials ;  and  the  total 
amount  of  combustible  materials  which  exists  on  its  surface  is, 
comparatively,  very  small.    That  which  exists  naturally  consists 
almost  entirely  of  carbon  and  its  compounds,  —  such  as  coal, 


COMBUSTION.  123 

naphtha,  and  wood ;  and  all  these  substances  are  the  results  of 
vegetable  growth,  either  of  the  present  age  or  of  earlier  geo- 
logical epochs.  Moreover,  whatever  subsequent  changes  the 
material  may  have  undergone,  it  was  all  originally  prepared 
by  the  plant  from  the  carbonic  acid  and  water  of  our  atmos- 
phere ;  for,  in  the  economy  of  nature,  these  products  of  com- 
bustion have  been  made  the  food  of  the  vegetable  world.  The 
sun's  rays,  acting  on  the  green  leaves  of  the  plant,  exert  a  mys- 
terious power,  which  decomposes  carbonic  anhydride,  and  per- 
haps also  water ;  and,  as  the  result  of  this  process,  oxygen  is 
returned  to  the  atmosphere,  while  carbon  and  hydrogen  are 
stored  up  in  the  growing  tissues  of  the  plant.  The  sun  thus 
undoes  the  work  of  combustion,  and  parts  the  atoms  which  the 
chemical  affinities  had  drawn  together.  In  doing  this,  the 
sun  exerts  an  enormous  power ;  and  the  work  which  it  thus  ac- 
complishes is  the  precise  measure  of  the  calorific  power  of  the 
combustible  material,  which  it  then  prepares.  When  we  wind 
up  the  weight  of  a  clock,  we  exert  a  certain  power  which  reap- 
pears in  its  subsequent  motions ;  and  so,  when  the  sun's  rays 
part  these  atoms,  the  great  power  it  exerts  is  again  called  into 
action,  when  in  the  process  of  combustion  the  atoms  reunite. 
Moreover,  what  is  true  of  calorific  power  is  true  of  all  mani- 
festations of  power  on  the  surface  of  the  earth.  Every  form 
of  motion  is  sustained  by  the  running  down  of  some  weight 
which  the  sun  has  wound  up ;  and,  according  to  the  best  theory 
we  can  form,  the  sun's  power  itself  is  sustained  by  the  gradual 
falling  of  the  whole  mass  of  the  solar  system  towards  its  com- 
mon centre.  However  varying  in  its  manifestation,  all  power 
in  its  essence  is  the  same,  and  the  total  amount  of  power  in  the 
universe  is  constant. 

65.  Heat  of  Chemical  Combinations.  —  The  heat  of  combus- 
tion is  only  a  striking  manifestation  of  a  very  general  principle, 
which  holds  true  in  all  chemical  changes.  It  would  appear 
that  whenever,  in  a  chemical  reaction,  atoms  or  molecules  are 
drawn  together  by  their  mutual  affinities,  a  certain  amount  of 
moving  power  is  developed,  which  takes  the  form  of  heat ;  and 
whenever,  on  the  other  hand,  these  same  atonas  or  molecules 
are  drawn  apart  by  the  action  of  some  superior  force,  the  same 
amount  of  moving  power  is  expended,  and  heat  disappears. 
Every  chemical  reaction  is  a  mixed  effect  of  such  combina- 


124  COMBUSTION.9 

tions  and  decompositions,  and  it  is  simply  a  complex  problem  in 
the  mechanical  theory  of  heat  to  determine  what  must  be  in 
any  case  the  *  thermal  effect.  The  numerous  facts  with 
which  we  are  acquainted  in  regard  to  the  heat  of  chemical 
combination  generally  agree  with  the  mechanical  theory  ;  and, 
where  the  facts  do  not  appear  to  conform  to  it,  the  discrepancy 
probably  arises  from  our  ignorance  of  the  nature  of  the  chem- 
ical change  in  question.  It  would  be  incompatible  with  our 
design  to  discuss  these  facts  in  this  book.  It  must  be  sufficient 
to  state  a  few  general  results,  which  may  be  summed  up  in  the 
following  propositions :  — 

First.  The  heat  absorbed  in  the  decomposition  of  a  com- 
pound is  equal  to  the  heat  evolved  in  its  formation,  provided 
the  initial  and  the  final  states  are  the  same. 

Second.  The  heat  evolved  in  a  series  of  successive  chemical 
changes  is  equal  to  the  sum  of  the  quantities  which  would  be 
evolved  in  each  separately,  provided  the  bodies  are  finally 
brought  into  identical  conditions. 

Third.  The  difference  between  the  quantities  of  heat  evolved 
in  two  series  of  changes  starting  from  two  different  states,  but 
ending  in  the  same  final  state,  is  equal  to  that  which  is  evolved 
or  absorbed  in  passing  from  one  initial  condition  to  the  other. 

For  example,  if  a  body  m  evolves  a  certain  amount  of  heat 
in  uniting  with  n  to  form  m  n,  and  if  the  body  m  n  is  decom- 
posed by  a  third  body  p,  so  that  m  p  is  formed,  the  quantity 
of  heat  evolved  in  this  last  reaction  is  less  than  that  which 
would  be  evolved  in  the  direct  union  of  m  and  p  by  the  amount 
evolved  in  the  formation  of  m  n. 

All  these  propositions,  however,  are  but  special  cases  under 
a  more  general  principle  which  is  at  the  basis  of  the  whole 
mechanical  theory  of  heat,  and  which  may  be  enunciated  as 
follows:  Whenever  a  system  of  bodies  undergoes  chemical 
or  physical  changes,  and  passes  into  another  condition,  what- 
ever may  have  been  the  nature  or  succession  of  the  changes, 
the  quantity  of  heat  evolved  or  absorbed  depends  solely  on  the 
initial  and  final  conditions  of  the  system,  provided  no  mechan- 
ical effect  has  been  produced  on  bodies  outside. 


COMBUSTION.  125 

Questions  and  Problems. 

1.  How  many  times   more   space  does  the   carbonic   anhydride 
formed  by  burning  charcoal  (Sp.  Gr.  =  2)  occupy  than  the  char- 
coal burnt  ? 

Ans.  One  cubic  centimetre  or  two  grammes  of  charcoal  yields 
3.720  litres.  Hence  the  gas  occupies  3,720  times  the  volume 
of  the  charcoal. 

2.  How  many  litres  of  oxygen  gas  are  required  to  burn  one  litre 
of  alcohol  vapor,  and  how  many  litres  of  aqueous  vapor,  and  how 
many  of  carbonic  anhydride,  will  be  formed  in  the  process  ? 

Ans.  3  litres  of  oxygen,  3  litres  of  aqueous  vapor,  2  litres  of  car- 
bonic anhydride. 

3.  Given  the  symbol  of  alcohol  CZHQ0  to  find  its  calorific  power. 
Ans.  6,572  units,  or  7,200  units,  assuming  that  the  steam  formed 

was  condensed. 

4.  The  composition  of  dried  peat  is  as  follows :  Carbon,  625.4 ; 
Hydrogen,  68.1  ;  Oxygen,  292.4  ;  Nitrogen,  14.1.     Find  the  calor- 
ific power.  Ans.  5,521  units. 

5.  Find  the  calorific  intensity  of  marsh  gas  burnt  in  oxygen. 

CJJ4  +  20=0  =  CO,  +  2H.20 

Calorific  power  of  marsh  gas,  13,063.     Specific  heat  of  steam,  0.4805 ; 
of  CO,,  0.2164.  Ans.   7,793. 

6.  Find  the  calorific  intensity  of  olefiant  gas  burnt  in  oxygen. 

C2ff4  +  3OO  =  2002  +  2R20 

Calorific  power  of  C2fiT4  11,858.     Specific  heat  of  steam  and  car- 
bonic anhydride  as  in  last  problem.  Ans.  9,136°. 

7.  Find  the  calorific  intensity  of  marsh  gas  and  olefiant  gas  burnt 
in  air.     Besides  the  data  already  given,  we  have  also  specific  heat  of 
nitrogen  0.244.  Ans.  2,662°,  and  2,916°. 


CHAPTER    XIII. 

MOLECULAR   WEIGHT   AND    CONSTITUTION. 

66.  Determination  of  Molecular  Weights.  —  It  has  already 
been  stated  that  the  molecular  weight  of  a  substance  is  an 
essential  element  in  fixing  its  symbol  and  in  judging  of  its 
chemical  relations,  but  until  now  the  student  has  not  possessed 
the  knowledge  necessary  in  order  to  understand  the  methods 
by  which  this  important  constant  is  determined. 

Whenever  the  substance  is  a  gas,  or  is  capable  of  being  vola- 
tilized without  decomposition  at  a  manageable  temperature,  we 
always  ascertain  the  molecular  weight  from  the  specific  gravity 
on  the  principle  already  several  times  enforced  (§  17).  The 
problem  then  resolves  itself  into  finding  the  specific  gravity  of 
the  substance  in  the  state  of  gas.  The  methods  used  in  such 
cases  are  described  on  page  21,  and  more  in  detail  in  the  au- 
thor's work  on  Chemical  Physics  (330  et  seq.),  and  in  the  same 
book  tables  are  given  which  very  greatly  facilitate  the  calcula- 
tion of  the  results.  The  specific  gravity  of  the  gas  or  vapor 
having  been  found  by  either  of  these  methods,  and  referred  to 
hydrogen  gas  as  the  unit,  the  molecular  weight  of  the  substance 
is  simply  twice  the  number  thus  determined.  But  in  applying 
this  important  principle,  on  which  our  modern  chemical  philoso- 
phy so  greatly  rests,  two  precautions  are  essential. 

It  is  only  true  that  equal  volumes  of  all  substances  contain 
the  same  number  of  molecules  when  they  are  in  the  condition 
of  true  gases.  Now,  while  some  substances,  like  alcohol,  assume 
this  condition  at  temperatures  only  a  few  degrees  above  their 
boiling  point,  at  least  nearly  enough  for  all  practical  pur- 
poses, others,  like  acetic  acid,  only  attain  it  at  temperatures  one 
or  two  hundred  degrees  above  their  boiling  point,  and  others 
still,  like  sulphur,  only  at  the  very  highest  temperatures  at 
which  we  have  been  able  to  experiment.  For  this  reason,  the 
specific  gravity  of  sulphur  vapor  was  for  a  long  time  an  anomalous 
fact  in  the  science,  and  it  was  not  until  St.  Clair  Deville,  by 


MOLECULAR  WEIGHT  AND   CONSTITUTION.  127 

using  a  porcelain  globe,  succeeded  in  determining  its  specific 
gravity  at  a  very  high  temperature,  that  its  value  was  found  to 
correspond  with  the  probable  molecular  weight,  and  it  is  pos- 
sible that  a  similar  anomaly  which  still  exists  in  the  case  of 
phosphorus  and  arsenic  may  be  due  to  the  same  cause. 

The  chemist,  however,  can  always  have  a  sure  criterion  of 
the  condition  of  any  vapor  whose  specific  gravity  he  is  deter- 
mining by  repeating  his  experiment  at  a  somewhat  higher  tem- 
perature. If  the  second  result  does  not  agree  with  the  first,  it 
is  a  proof  that  the  vapor  is  not  yet  in  a  proper  condition,  and 
that  the  temperature  employed  in  the  experiment  was  too  low. 
A  series  of  determinations  of  the  specific  gravity  of  the  vapor 
of  acetic  acid  made  by  Cahours  furnish  an  excellent  illustra- 
tion of  the  importance  of  the  precaution  we  are  discussing,  and 
will  also  point  out  another  important  relation  of  this  whole  sub- 
ject. This  acid  when  in  the  most  concentrated  state  boils  at 
120°,  and  the  specific  gravity  of  its  vapor  referred  to  hydrogen 
at  the  same  temperature  and  pressure  was  found  to  have  the 
following  values  at  the  temperatures  annexed :  — 

At  125  45.90  At  170  35.30  At  240  30.16 

"  130  44.82  "    180  35.19  "    270  30.14 

"  140  41.96  "    190  34.33  "    310  30.10 

"  150  39.37  "    200  32.44  "    320  30.07 

"  160  37.59  "    220  30.77  «    336  30.07 

It  will  be  noticed  that,  as  the  temperature  increases,  the 
specific  gravity  diminishes,  at  first  very  rapidly,  afterwards 
more  slowly,  and  does  not  become  constant  until  the  tempera- 
ture has  risen  200°  above  the  boiling  point,  when  we  have  the 
true  specific  gravity  of  acetic  acid  m  the  state  of  gas.  This 
gives  for  the  molecular  weight  of  acetic  acid  60  very  nearly, 
which  corresponds  to  the  received  formula,  C.2ff402.  The  slight 
difference  between  the  theoretical  and  the  observed  results 
may  be  in  part  due  to  errors  of  observation,  but  is  most  prob- 
ably to  be  referred  to  the  same  cause  which  determines  even 
in  the  permanent  gases,  when  under  the  atmospheric  pressure, 
a  variation  from  Mariotte's  law.  We  do  not  expect>  moreover, 
to  find  from  the  specific  gravity  the  exact  molecular  weight. 
The  precise  value  is  determined  by  the  results  of  analysis,  which 
are,  as  a  rule,  far  more  accurate,  and  the  specific  gravity  is 


128 


MOLECULAR  WEIGHT  AND   CONSTITUTION. 


only  used  to  decide  which  of  several  possible  multiples  must  he 
the  true  value.     (Compare  carefully  §  23.) 

67.  Disassociation.  —  But,  besides  taking  care  that  the  tem- 
perature is  sufficiently  high  to  bring  the  substance  we  are 
studying  into  the  condition  of  a  true  gas,  we  must  look  out  that 
the  compound  is  not  decomposed  in  the  process.  It  is  now  well 
known  that  at  very  high  temperatures  the  disassociation  of 
the  elements  of  a  compound  body  is  a  constant  result,  and  it  is 
probable  that  in  some  cases  the  same  effect  is  produced  at  the 
much  lower  temperatures  which  are  employed  in  the  determi- 
nation of  vapor  densities.  The  specific  gravity  of  the  vapor 
of  ammonic  chloride,  instead  of  being  26.75,  as  we  should  ex- 
pect from  the  undoubted  .weight  of  its  molecule,  Nff±Cl,  is 
only  about  one  half  of  this  amount ;  and  the  reason  probably  is, 
that,  when  heated,  the  molecule  breaks  into  two,  and  in  conse- 
quence the  volume  of  the  vapor  doubles. 


It  is  very  difficult,  however,  to  obtain  any  further  evidence 
that  such  a  change  has  taken  place ;  for,  as  soon  as  the  tempera- 
ture falls,  the  molecules  recombine  in  assuming  the  solid  condi- 
tion, and  all  the  phenomena  attending  the  change  of  state  are 
precisely  the  same  as  those  observed  in  any  other  volatile 
body.  Indeed,  although  many  very  ingenious  experiments 
have  been  made  with  a  view  of  settling  the  question,  it  is  still 
uncertain,  not  only  in  this,  but  also  in  several  other  cases, 
whether  disassociation  has  taken  place  or  not.  The  question 
is  of  great  importance  to  the  theory  of  chemistry.  If  disasso- 
ciation does  not  take  place,  the  cases  referred  to  are  exceptions 
to  the  law  of  equal  molecular  volumes,  and  specific  gravity  can 
no  longer  be  regarded,  as  now,  the  sole  measure  of  molecular 
weight.  If,  however,  it  can  be  proved  that  such  a  change  does 
take  place,  then  the  unity  of  our  present  theory  is  preserved, 
and  the  chemist  has  only  to  guard  against  this  cause  of  error 
in  his  experiments. 

68.  Indirect  Determination  of  Molecular  Weight.  —  Al- 
though our  modern  chemical  theories  rest  in  great  measure  on 
the  molecular  weight  of  a  few  typical  compounds  determined, 


MOLECULAR  WEIGHT  AND  CONSTITUTION.  129 

at  least  approximately,  by  their  specific  gravities,  yet  it  is  only 
in  a  comparatively  few  cases  that  we  are  able  to  refer  the 
molecular  weight  of  a  substance  directly  to  this  fundamental 
measure.  Most  substances  are  so  fixed,  or  so  easily  decom- 
posed by  heat,  that  it  is  impossible  to  determine  the  specific 
gravity  of  their  vapor,  even  when  such  a  condition  is  possible. 
In  these  cases,  however,  we  endeavor  to  refer  the  molec- 
ular weight  indirectly  to  the  fundamental  measure,  by  estab- 
lishing a  relation  of  chemical  equivalency  between  the  sub- 
stance whose  molecular  weight  is  sought  and  some  closely 
allied  volatile  substance  whose  molecular  weight  has  been  pre- 
•  viously  determined  in  the  manner  described  above.  A  few  ex- 
amples will  make  the  application  of  this  principle  intelligible. 

It  is  required  to  determine  the  molecular  weight  of  nitric 
acid.  A  careful  study  of  the  numerous  nitrates  leads  to  the 
conclusion  that  this  acid,  like  hydrochloric  acid,  ffCl,  con- 
tains but  one  atom  of  replaceable  hydrogen.  For  example,  we 
find  but  one  potassic  nitrate  and  one  sodic  nitrate,  whereas  we 
should  expect  to  find  several,  if  the  acid  were  polybasic. 
Hence  we  conclude  that  one  molecule  of  argentic  nitrate,  like 
one  molecule  of  argentic  chloride,  AgCl,  contains  but  one 
atom  of  silver.  Next,  we  analyze  argentic  nitrate,  and  find 
that  100  parts  of  the  salt  contain  63.53  parts  of  silver.  We 
know  the  atomic  weight  of  silver,  1 08,  and  evidently  this  must 
bear  the  same  relation  to  the  molecular  weight  of  argentic 
nitrate  that  63.53  bears  to  100.  But  63.53  :  100  =  108  : 
#=170,  which  is  the  molecular  weight  of  argentic  nitrate, 
and,  since  the  molecule  of  nitric  acid  differs  from  that  of  argen» 
tic  nitrate  only  in  containing  an  atom  of  hydrogen  in  place  of 
the  atom  of  silver,  its  own  weight  must  be  170  —  108  -f-  1 
=  63. 

It  is  required  to  determine  the  molecular  weight  of  sul- 
phuric acid.  A  comparison  of  the  different  sulphates  shows 
that  sulphuric  acid  is  dibasic.  We  find  two  sulphates  of  potas- 
sium and  sodium,  an  acid  sulphate  and  a  neutral  sulphate,  and 
hence  we  conclude  that  this  acid  contains  two  replaceable 
atoms  of  hydrogen,  and  hence  that  one  molecule  of  neutral 
potassic  sulphate  contains  two  atoms  of  potassium.  In  ana- 
lyzing potassic  sulphate  it  appears  that  100  parts  of  the  salt 
contain  44.83  parts  of  potassium,,  and  evidently  this  weight 
9 


130  MOLECULAR  WEIGHT  AND   CONSTITUTION. 

bears  the  same  relation  to  100  that  the  weight  of  two  atoms  of 
potassium  bears  to  the  weight  of  the  molecule  of  potassic  sul- 
phate. Thus  we  have,  — 

44.83  :  100  =  78  :  x  =  174  ;  the  M.  W.  of  Potassic  Sulphate, 
and  174  —  78  -f  2  =  98  ;  the  M.  W.  of  Sulphuric  Acid. 

By  a  similar  course  of  reasoning  we  may  deduce  from  the 
results  of  analysis,  and  from  the  general  chemical  rela- 
tions, the  molecular  weight  of  any  other  acid  or  base.  If 
there  is  any  question  in  regard  to  the  basicity  of  the  acid  or 
the  acidity  of  the  base,  there  will  be  the  same  question  as  to 
the  molecular  weight  ;  but  we  cannot  be  led  far  into  error,  for 
the  true  weight  will  be  some  simple  multiple  or  submultiple  of 
the  one  assumed,  and  the  progress  of  science  will  sooner  or 
later  correct  our  mistake.  From  the  molecular  weight  of  any 
acid  we  easily  deduce  the  molecular  weights  of  all  its  salts. 

When  the  substance  is  not  distinctively  an  acid  or  a  base,  but 
is  capable  of  entering  into  combination  with  other  bodies,  we 
can  frequently  discover  its  molecular  weight  by  determining 
experimentally  how  much  of  this  substance  is  equivalent  to  a 
known  weight  of  some  allied  but  volatile  substance  whose 
molecular  weight  is  known.  Thus  ammonia  gas,  whose  molec- 
ular weight  is  one  of  the  best-established  data  of  chemistry, 
enters  into  direct  union  with  a  compound  of  platinic  chloride 
and  hydrochloric  acid  (Pt  CltiH2)  to  form  a  definite  crystalline 
salt  whose  composition  is  exactly  known. 


PtClGH2  +  2NJJ3  =  PtCk(NHt)f  [61] 

Now  a  very  large  number  of  substances  allied  to  ammonia 
form  with  this  same  platinum  salt  equally  definite  products,  so 
that  by  simply  determining  the  weight  of  platinum  in  these 
compounds,  which  is  very  easily  done,  their  molecular  weights 
may  at  once  be  referred  to  the  molecular  weight  of  ammonia. 

Lastly,  if  other  means  fail,  we  may  sometimes  discover  the 
molecular  weight  of  a  compound  by  carefully  studying  the  reac- 
tions by  which  it  is  formed  or  decomposed,  and  inferring  the 
weight  of  the  compound  from  that  of  its  factors  or  products.  We 
seek  to  express  the  reaction  in  the  simplest  possible  way,  and 
give  that  value  to  the  molecular  weight  which  best  satisfies  the 


MOLECULAR  WEIGHT  AND  CONSTITUTION.  131 

chemical  equation.  Evidently,  however,  such  results  are  less 
trustworthy  than  those  obtained  by  either  of  the  other  methods. 

69.  Constitution  of  Molecules.  —  It  is  a  favorite  theory  with 
some  chemists  that  no  molecule  can  exist  in  a  free  condition 
with  any  of  its  affinities  unsatisfied,  but  those  who  hold  this 
view  are  compelled  to  admit  that  two  points  of  attraction  in 
the  same  atom  may,  in  certain  cases,  neutralize  each  other. 
Hence,  they  would  distinguish  between  a  dyad  atom  like  that 
of  oxygen  (•  •),  with  its  affinities  open,  and  a  dyad  atom  like 
that  of  mercury  (~  -),  with  its  affinities  closed  through  their  own 
mutual  attraction.  The  first  could  not  exist  in  a  free  condition, 
while  the  last  could.  In  like  manner  any  atom,  having  an  even 
number  of  points  of  attraction,  can  exist  in  a  free  state  because 
all  its  affinities  may  be  satisfied  within  itself;  but  an  atom  hav- 
ing an  uneven  number  of  points  cannot,  for  at  least  one  of  its 

affinities  must  be  open  as  is  shown  by  the  symbol  (^ •).  As 

thus  interpreted  it  must  be  admitted  that  the  theory  explains 
many  facts. 

For  example,  among  the  univalent  elements,  chlorine,  bro- 
mine and  iodine  are  all  known  to  have  molecules  consisting  of 
two  atoms.  So,  also,  the  molecule  of  cyanogen  gas  consists  of 
two  atoms  of  the  radical  ON,  and  the  same  is  true  of  ethyl, 
propyl,  &c.,  at  least  if  the  hydrocarbons  so  named  have  really 
the  constitution  first  assigned  to  them. 

Passing  next  to  the  dyads,  we  find  that,  while  oxygen,  sulphur, 
selenium  and  tellurium  have  molecules  consisting  of  two  atoms, 
the  metals  mercury  and  cadmium,  and  the  radicals  ethylene, 
propylene,  &c.  (O2ff4  and  CgZQ,  have  molecules  which  coincide 
with  their  atoms. 

Of  the  well-defined  triad  elements  none  are  volatile,  but  the 
two  triad  radicals  which  have  been  obtained  in  a  free  state' — 
allyl1  (Csff5)  and  kakodyl  ((Cff3)2As)  —  both  have  double 
atomic  molecules. 

In  like  manner  none  of  the  tetrad  elements  are  volatile, 
and  the  only  tetrad  radicals  known  in  a  free  state  have  single 
atomic  molecules. 

Of  the  pentad  elements  nitrogen  has  a  molecule  of  two 
atoms,  while  phosphorus  and  arsenic  have  molecules  of  four 

1  See  page  78,  Problem  7. 


132  MOLECULAR  WEIGHT  AND   CONSTITUTION. 

atoms.  No  compound  radicals  of  this  order  are  known  in  a 
free  state. 

Lastly,  the  only  hexad  radical  known  in  a  free  state,  benzine, 
C6ff6,  has  a  molecule  which  coincides  with  its  atom. 

Thus  it  appears  that  in  general  the  theory  is  sustained  by  the 

facts.     Nevertheless,  there  are  several  well-marked  exceptions 

in  i 

to  it.     Thus  the  well-known  compounds  NO  and  N02  have 

molecules  which  act  as  radicals  of  uneven  atomicities  and  yet 
contain  but  one  complex  atom.  We  must  be  careful,  therefore, 
not  to  give  too  much  weight  to  this  hypothesis,  but  still  it  may 
be  useful  in  co-ordinating  facts.  It  leads  at  once  to  three  gen- 
eral principles  which  will  be  found  to  be  almost  universally 
true. 

The  first  is  that  the  sum  of  the  atomicities  of  the  atoms  of 
every  molecule  is  an  even  number. 

The  second  is  that  the  atomicity  of  any  radical  is  an  odd 
or  even  number  according  as  the  sum  of  the  atomicities  of 
its  elementary  atoms  is  odd  or  even. 

The  third  is  that  the  quantivalence  of  elementary  atoms 
must  be,  as  stated  on  page  59,  either  even  or  odd.  They  are 
artiads  or  perissads,  and  the  two  characters  can  never  be  mani- 
fested by  the  same  elements. 

It  has  also  been  a  question  among  chemists  whether  molec- 
ular combination  was  possible  ;  in  other  words,  whether  it  is 
possible  for  molecules  of  different  kinds  to  combine  chemically, 
each  preserving  its  integrity  in  the  compound.  Some  of  the 
advocates  of  the  unitary  theory,  in  the  reaction  against  the 
dualistic  system,  have  been  inclined  to  doubt  the  possibility  of 
such  compounds,  and  have  attempted  to  represent  the  symbols 
of  all  compounds  in  a  single  molecular  group ;  but  any  ante- 
cedent improbability,  on  theoretical  grounds,  is  far  more  than 
outweighed  by  the  evidence  of  a  large  number  of  compounds 
whose  constitution  is  most  simply  explained  on  the  hypothesis 
of  molecular  combination.  For  example,  in  the  crystalline  salts 
it  is  impossible  to  doubt  that  the  water  exists  as  such,  not  as  a 
part  of  the  salt  molecule,  but  combined  with  it  as  a  whole.  So, 
also,  there  are  a  number  of  double  salts  whose  constitution  is 
most  simply  explained  on  a  similar  hypothesis,  and,  in  the  pres- 
ent state  of  the  science,  it  seems  unnecessary  to  complicate 
their  symbols  by  forcing  them  into  the  unitary  mould.  It  is  a 


MOLECULAR  WEIGHT  AND  CONSTITUTION.  133 

characteristic  of  such  molecular  compounds  as  are  here  assumed, 
that  the  force  which  holds  together  the  molecules  is  much  feebler 
than  that  which  binds  together  the  atoms  in  the  molecule.  When 
the  molecular  attraction  is  very  strong,  it  is  probable  that  in 
almost  all  cases  the  different  molecules  coalesce  into  one ;  and 
between  the  extreme  limits  we  find  compounds  in  which  it  is 
difficult  to  determine  whether  true  molecular  combination  ex- 
ists or  not.  Such  coalescing  of  distinct  molecules  seems  always, 
however,  to  be  attended  with  a  greater  development  of  heat,  and, 
in  general,  with  a  more  marked  manifestation  of  physical  ener- 
gies, than  usually  attends  either  molecular  aggregation  or  atomic 
metathesis. 

In  the  notation  of  this  book  molecular  combination  is  indi- 
cated by  writing  together  the  symbols  of  the  different  molecules 
thus  united,  but  separating  these  symbols  by  periods.  Thus 
the  symbols  ^KCLPtCl^  and  3NaF.SbF3  represent  compounds 
of  this  class. 

70.  Isomerism,  Allotropism,  Polymorphism.  —  We  should 
infer  from  the  doctrine  of  chemical  types  that  the  same  atoms 
might  be  grouped  together  in  different  ways,  so  as  to  form 
different  molecules  which  in  their  aggregation  would  present 
essentially  distinct  qualities.  Hence,  we  should  expect  to  find 
distinct  substances  having  the  same  composition ;  and  in  fact 
our  science,  organic  chemistry  especially,  is  rich  in  examples 
of  this  kind.  Such  substances  are  said  to  be  isomeric.  and  the 
phenomenon  is  called  isomerism.  There  are  different  phases 
of  isomerism,  which  it  will  be  well  to  distinguish,  not  so  much 
on  account  of  any  essential  differences  in  the  phenomena  as  in 
order  to  make  ourselves  better  acquainted  with  its  manifesta- 
tions. 

In  the  first  place,  we  have  examples  of  isomeric  bodies 
having  the  same  centesimal  composition,  but  showing  no  rela- 
tion to  each  other  in  their  properties  or  in  their  chemical 
reactions.  Sometimes  we  have  assigned  to  them  the  same 
formula,  but  in  other  cases  the  symbol  of  one  is  a  simple 
multiple  of  that  of  the  other.  Thus  aldehyde  and  oxide  of 
ethylene  have  both  the  symbol  C2Jf4  0 ;  cane  sugar  and  gum 
arabic,  the  common  formula  O^H.^  0n ;  lactic  acid,  the  formula 
C3ffiO3i  and  glucose,  C6//i206.  These  compounds  bear  no 
resemblance  to  each  other,  and  have  no  relations  in  common 


134  MOLECULAR  WEIGHT  AND  CONSTITUTION. 

save  the  single  fact  that  their  centesimal  composition  is  the 
same. 

In  the  second  place,  we  have  numerous  examples  of  isomeric 
compounds,  which,  with  the  same  centesimal  composition,  have 
also  the  same  molecular  weight,  and  whose  molecules,  therefore, 
consist  of  the  same  number  of -atoms,  but  where  a  fundamental 
difference  in  the  grouping  of  the  atoms  may  be  inferred  from 
the  nature  and  products  of  the  chemical  reactions,  by  which  such 
isomeric  compounds  are  formed  or  decomposed.  Thus,  for  ex- 
ample, ethylic  formiate  (C2ff5)-0-(CffO)  has  exactly  the  same 
composition  and  molecular  weight  as  methylic  acetate  (CH^y- 
0~(  O^ff3  0).  The  same  is  true  of  cyanic  ether  and  cyanetholine, 
whose  symbols  have  already  been  given  (page  77)  in  connec- 
tion with  the  reactions,  which  indicate  their  molecular  constitu- 
tion, and  another  still  more  remarkable  case  will  be  found  in 
Part  II.  of  this  work  [164]  and  [165]. 

In  the  third  place,  we  have  several  groups  of  isomeric  com- 
pounds, especially  among  the  hydrocarbons,  which  have  the 
same  general  properties  and  the  same  percentage  composition, 
but  which  differ  from  each  other  in  their  molecular  weights ;  so 
that  the  symbol  of  one  is  a  multiple  of  that  of  the  rest.  The 
hydrocarbons  ethylene  C2ff^  propylene  C&ffG^  butylene  C4ff^ 
form  a  group  of  this  kind.  Compounds  of  this  class  are  fre- 
quently called  polymeric,  and  sometimes  the  heavier  com- 
pounds may  be  regarded  as  condensed  forms  of  the  lighter. 

Lastly,  we  may  distinguish  still  a  fourth  class  of  isomeric 
compounds  which  have  the  same  general  properties,  the  same 
symbol,  and  the  same  general  system  of  reactions,  but  which 
differ  in  a  few  marked  qualities,  physical  or  chemical,  and 
which  preserve  these  characteristics  to  a  greater  or  less  extent  in 
their  compounds.  The  two  forms  of  toluic  acid,  C8HS0^  be- 
long to  this  class,  and  such  compounds  are  isomeric  in  the 
fullest  sense  of  the  word. 

In  all  the  above  examples  the  differences  between  the  iso- 
meric compounds  are  sufficiently  great  to  lead  chemists  to 
assign  to  each  a  distinct  name.  When,  however,  the  differ- 
ences are  not  sufficiently  great  to  justify  a  distinct  name,  the 
two  bodies  are  said  to  be  different  allotropic  states  of  the  same 
substance.  Thus  there  are  two  varieties  of  tartaric  acid ;  the 
first  of  which  deviates  the  plane  of  polarization  of  a  ray  of  light 


MOLECULAR   WEIGHT   AND   CONSTITUTION.  135 

to  the  left,  while  the  second  deviates  it  to  the  right ;  but  since 
in  almost  every  other  respect  these  two  bodies  are  identical, 
we  do  not  speak  of  them  as  different  substances,  but  merely  as 
different  allotropic  states  of  tartaric  acid.  There  are  also  three 
other  varieties  of  tartaric  acid,  but  these  differ  so  greatly  from 
the  normal  acid  in  crystalline  form,  in  solubility,  and  also  in 
other  relations,  that  they  may  fairly  be  regarded  as  distinct 
substances. 

Again,  there  are  many  substances  where  the  difference  of 
state  or  aUotropism  is  associated  with  difference  of  crystalline 
form  ;  and  when  this  difference  of  form  is  fundamental,  the 
substance  is  said  to  be  dimorphous  or  trimorphous,  as  the  case 
may  be,  and  the  phenomenon  is  called  polymorphism.  Thus 
common  calcic  carbonate  crystallizes  in  two  fundamentally  dis- 
tinct forms,  corresponding  to  the  two  mineralogical  species, 
calcite  and  aragonite.  Such  difference  of  form,  however,  is 
invariably  accompanied  by  a  marked  difference  of  properties, 
so  that  polymorphism  is  merely  one  of  the  indications  of  allo- 
tropism. 

Differences  of  condition  similar  to  those  we  have  described 
manifest  themselves  even  more  markedly  among  elementary 
substances ;  and  indeed  the  word  allotropism  was  first  applied 
to  phenomena  of  this  last  class.  Thus  there  are  two  allotropic 
states  of  phosphorus,  which  differ  so  much  from  each  other  that 
no  one  would  suspect  from  their  external  characters  that  there 
was  any  identity  between  them,  and  to  these  two  states  corre- 
spond two  fundamentally  different  crystalline  forms.  In  some 
cases  the  differences  between  the  allotropic  states  of  the  same 
element  are  far  greater  than  any  which  are  seen  between  the 
most  unlike  isomeric  compounds.  No  substances  could  be 
better  defined  by  well-marked  and  utterly  distinct  qualities 
than  diamond,  plumbago,  and  charcoal,  and  yet  they  are  all 
three  allotropic  modifications  of  the  one  elemental  substance 
we  call  carbon  ;  and  such  phenomena  as  these  give  us  strong 
grounds  for  believing  that  our  present  elements  may  have  a 
composite  structure. 


136  MOLECULAR  WEIGHTS  AND  CONSTITUTION. 


Questions  and  Problems. 

1.  What  are  the  molecular  weights  of  alcohol  and  camphor  as  de- 
duced from  the  results  of  the  £jtj.  (B>t.  determinations  given  on  page 
23? 

Ans.  45.5  and  155,  which,  although  not  closely  agreeing  with  the 
theoretical  numbers,  enables  us  to  decide  that  the  symbols 
of  these  compounds  are  C2H60  and  CloHl60  as  the  simplest 
interpretation  of  the  analyses  would  indicate. 

2.  At  the  temperature  of  470°  the  gm.  (J$r.  of  the  vapor  of  sul- 
phuric acid  is  approximately  1.697.    How  does  this  result  agree  with 
the  generally  received  symbol  of  this  compound,  and  how  do  you 
explain  the  discrepancy  ? 

3.  A  study  of  the   different  tartrates  has  led  to  the  conclusion 
already  expressed  that  tartaric  acid,  although  tetratomic,  is  dibasic. 
It  also  appears  that  one  hundred  parts  of  neutral  argentic  tartrate 
yield  when  ignited   55.39  parts  of  metallic  silver.      Required  the 
molecular  weight  of  tartaric  acid.  Ans.  1 76. 

4.  An  hundred  parts  of  baric  oxide,  BaO,  (whose  composition  is 
assumed  to  be  known)  yield  when  treated  with  sulphuric  acid  152.3 
parts  of  baric  sulphate.     Further  it  is  assumed,  as  the  result  of  care- 
ful study,  that  sulphuric  acid  is  dibasic,  and  the  metal  barium  a  biva- 
lent radical.     Required  the  molecular  weight  of  sulphuric  acid. 

Ans.  98. 

5.  The  well-known    base  aniline  gives  with  platinic  chloride  a 
definite  crystalline  product,  one  hundred  parts  of  which  yield  on 
ignition  32.99  parts  of  platinum.     Required  the  molecular  weight  cf 
aniline.     How  does  this  result  agree  with  the   gp.  (gr.  of  aniline 
vapor,  which  has  been  found  by  observation  to  be  3.210.  ? 

Ans.     93 ;  which  corresponds  to  gjj.  (g>r.  of  3.223. 

6.  The  base  triethylamine  gives  in  like  manner  a  platinum  salt, 
one  hundred  parts  of  which  yield  on  ignition  32.13  parts  of  plati- 
num.    Required  the  molecular  weight.  Ans.  101. 

7.  Compare  together  the  symbols  of  the  compounds  of  the  va- 
rious alcohol  radicals  on  pages  90  to  93  and  point  out  the  exam- 
ples of  isomerism. 


CHAPTER    XIV. 

CRYSTALLINE    FORMS. 

71.  Relations   to    Chemistry.  —  Almost     every     substance 
affects  a   definite  polyhedral  form,  although  it  may  manifest 
this  tendency  only  under  favorable  conditions.    Such  forms  are 
called  crystals,  arid  the  process  of  crystalline  growth,  or  de- 
velopment, is  called  crystallization.     The  one  essential  condi- 
tion of  crystallization  is  a  certain  freedom  of  motion,  and  crys- 
tals, more  or  less  perfect,  are  usually  formed  whenever  a  molten 
liquid  "  sets,"  or  a  solid  is  deposited  from  a  condition  of  solution 
or  of  vapor ;  and  in  each  case  the  slower  the  process  the  larger 
and  the  more  perfect  are  the  crystals.     The  crystalline  condi- 
tion is,  in  fact,  the  normal  state  of  solid  matter.    It  is  true  that 
there  are  a  few  substances  which,  like  glue,  are  only  known  in 
the  colloid  state;  but  in  most  of   the  so-called   colloid  sub- 
stances this  state  is  abnormal,  and  there  is  a  constant  tendency 
to  crystallization.    Moreover,  its  peculiar  crystalline  form  is  one 
of  the  most  characteristic,  and  apparently  one  of  the  most  es- 
sential, properties  of  a  substance,  and  is  therefore  of  great  value 
in  determining  its  chemical  affinities.    The  study  of  the  geomet- 
rical relations  of  these  forms  is,  however,  in  itself  a  separate 
science,  and  in  this  connection  we  can  only  dwell  on  the  few 
elementary  principles  of  the  subject  on  which  our  system  of 
chemical  classification  in  part  rests. 

72.  Definitions.  —  In  the  forms  of  crystals  the  idea  of  sym- 
metry is  the  great  controlling  principle.     Each  substance  fol- 
lows a  certain  law  of  symmetry,  which  seems  to  be  inherent, 
and  a  part  of  its  very  nature ;  and.  when,  from  any  cause,  the 
character  of  the   symmetry  changes,  the   substance  loses  its 
identity,  and,  even  if  its  chemical  composition  remains  the 
same,  it  becomes,  to  all  intents  and  purposes,  a  different  sub- 
stance.    In  every  crystal  the  symmetry  points  to  a  few  direc- 
tions, to  which  not  only  the  position  of  the  planes,  but  also  the 
physical  properties  of  the  body,  are  closely  related.    Certain  of 


138 


CRYSTALLINE  FORMS. 


Fig.  4. 


these  directions,  more  or  less  arbitrarily  chosen,  are  called  the 
axes  of  the  crystals,  and  a  crystalline  form  may  be  defined  as 
a  group  of  similar  planes  symmetrically  disposed  around  these 
axes.  As  is  evident  from  this  definition  a 
crystalline  form,  like  a  geometrical  form,  is 
a  pure  abstraction,  and  this  conception  is 
carefully  to  be  kept  distinct  from  the  idea 
of  a  crystal,  which  implies  not  only  a  cer- 
tain form,  but  also  a  certain  structure. 
Moreover,  in  by  far  the  larger  number  of 
cases  the  same  crystal  is  bounded  by  several 
forms.  Thus,  in  Fig.  4,  which  represents  a 
crystal  of  common  quartz,  the  planes  of  the 
prism  and  the  planes  of  the  pyramid  are 
distinct  crystalline  forms. 

73.  Systems  of  Crystals.  —  A  careful  study  of  the  forms  of 
crystals  has  shown  that  these  forms  may  be  classified  under  six 
crystalline  systems,  each  of  which  is  distinguished  by  a  peculiar 
plan  of  symmetry.     These  divisions,  it  is  true,  are  in  a  meas- 
ure arbitrary  ;  for  here,  as  elsewhere  in  nature,  no  sharp  dividing 
lines  are  found  ;  but  nevertheless  the  distinctions  on  which  the 
classification  rests  are  clearly  marked.     We  can  only  give  in 
this  book  a  very  imperfect  idea  of  these  several  plans  of  sym- 
metry by  representing  with  figures  a  few  of  the  more  charac- 
teristic forms  of  each. 

74.  First  or  Isometric  System.1  —  The  three  most  frequently 
occurring  forms  of  this  system  are  the  regular  octahedron,  the 


Fig.  5. 


Fig.  6. 


Fig.  7. 


rhombic  dodecahedron  and  the  cube,  Figs.  5,  6,  and  7.     These 
and  all  the  other  forms  of  the  system  may  be  regarded  as 


1  Called  also  monometric. 


CRYSTALLINE  FORMS. 


139 


grouped  around  three  equal  and  similar  axes  at  right  angles  to 
each  other,  and  hence  the  name  isometric  (equal  dimensions). 
They  present  the  same  symmetry  on  all  sides,  and  the  appear- 
ance of  the  form  is  identical,  whichever  axis  is  placed  in  a  ver- 
tical position.  In  this  system  no  variation  in  the  relative  posi- 
tions or  lengths  of  the  axes  is  possible,  for  this  would  change 
the  plan  of  symmetry  on  which  the  system  is  based. 

75.  Second  or  Tetragonal  System}-  —  The  plan  of  symmetry 
in  this  system  is  best  illustrated  by  the  square  octahedron,  Fig. 
8.  Of  this  form  the  basal  section,  Fig.  9,  is  a  square,  and  to 

Fig.  9. 
Fig.  8. 


this  fact  the  name  of  the  system  refers.  The  vertical  section, 
on  the  other  hand,  is  a  rhomb,  Fig  10.  Here,  as  in  the  first 
system,  the  forms  may  all  be  referred  to  three  rectangular  axes, 
but  only  two  have  the  same  length  ;  the  third  may  be  either 
longer  or  shorter  than  the  others.  The  last  is  the  dominant 
axis  of  the  form,  and  hence  we  always  place  it  in  a  vertical 
position  and  call  it  the  vertical  axis.  The  length  of  the  verti- 
cal axis  bears  a  constant  ratio  to  that  of  the  lateral  axes  in  all 
crystals  of  the  same  substance,  but  this  ratio  differs  very  greatly 
for  different  substances,  and  is  therefore  an  important  crystal- 
lographic  character.  The  familiar  square  prism  is  another  very 
characteristic  form  of  this  system. 

r.  11.  Fig.  12. 


Moreover,  the  planes  both  of  the  prism  and  of  the  octahedron 
may  have  different  positions  with  reference  to  the  lateral  axes, 
as  is  shown  by  the  two  basal  sections,  Figs.  11  and  12; 

-  Called  also  dimetric. 


140 


CRYSTALLINE  FORMS. 


and  this  leads  us  to  distinguish  two  square  prisms  and  two 
square  octahedrons,  one  of  which  is  said  to  be  the  inverse  of 
the  other. 

76.  Third  or  Hexagonal  System.  —  In  the  last  system  the 
planes  were  arranged  by  fours  around  one  dominant  axis,  while 
in  this  system  they  are  arranged  by  sixes.  The  most  character- 
istic forms  of  this  system  are  the  hexagonal  pyramid,  Fig.  13, 
and  the  hexagonal  prism,  Fig.  14.  The  basal  section  through 
either  of  these  forms  is  a  regular  hexagon,  Fig.  15,  and,  besides 

Fig.  13. 


Fig.  14. 


Fig.  15. 


the  dominant  or  vertical  axis,  we  also  distinguish  as  lateral  axes 
the  three  diagonals  of  this  hexagonal  section.  These  lateral 
axes  stand  at  right  angles  to  the  vertical  axis,  but  between 
themselves  they  subtend  angles  of  60°«  Here,  as  before,  the 
ratio  of  the  length  of  the  vertical  axis  to  the  common  length  of 
the  lateral  axes  has  a  constant  value  on  crystals  of  the  same 
substance,  but  differs  very  greatly  with  different  substances, 
the  vertical  axis  being  sometimes  longer  and  sometimes  shorter 

Fig.  17. 
Fig.  16. 


than  the  other  three.     The   rhombohedron,  Fig.  16,  and  the 
scalenohedron,  Fig.  17,  are  also  forms  of  this  system,  and  occur 


CRYSTALLINE  FORMS.  141 

even  more  frequently  than  the  more  typical  forms  first  men- 
tioned. Lastly,  a  difference  of  position  in  the  planes  of  the 
prism  or  pyramid  with  reference  to  the  lateral  axes  gives  rise 
in  this  system  to  the  same  distinction  between  the  direct  and 
the  inverse  forms  as  in  the  last. 

77.  Fourth  or  Orthorhombic  System.1  —  The  most  character- 
istic forms  of  this  system  are  the  rhombic  octahedron,  Fig.  18, 
and  the  right  rhombic  prism,  from  which  the  system  takes  its 
name.  The  three  principal  sections  of  the  octahedron,  repre- 
sented by  Figs.  19,  20,  and  21,  and  also  the  basal  section  of  the 

Fig.  18.  Fig.  19.  Fig.  20. 


prism,  are  all  rhombs,  whose  relations  to  the  form  are  indicated 
by  the  lettering  of  the  figures.  We  easily  distinguish  here  three 
axes  at  right  angles  to  each  other,  but  of  unequal  lengths,  and 
in  regard  to  the  ratios  of  these  lengths,  the  remarks  of  the  last 
two  sections  are  strictly  applicable. 

78.  Fifth  or  Monodinic  System. — The  forms  classed  together 
under  this  system  may  be  referred  to  three  unequal  axes,  one  of 
which  stands  at  right  angles  to  the  plane  of  the  other  two,  while 
they  are  inclined  to  each  other  at  an  angle,  which,  though  con- 
stant on  crystals  of  the  same  substance,  varies  very  greatly  with 
different  substances,  as  vary  also  the  relative  dimensions  of  the 
axes  themselves.  Fig.  22  represents  an  octahedron  of  this 
system,  and  Figs.  23  and  24  represent  two  sections  made 
through  the  edges  FF  and  DD'  of  this  form.  A  section 
through  the  edges  G  O  would  be  similar  to  Fig.  23,  and  these 
three  sections  give  a  clear  idea  of  the  relative  positions  of  the 
axes.  The  section,  Fig.  24,  containing  the  two  oblique  axes, 

l  Called  also  trimetric. 


142 


CRYSTALLINE  FORMS. 


is  called  the  plane  of  symmetry,  and  the  faces  on  all  monoclinic 
crystals  are  disposed  symmetrically  solely  with  reference  to  this 
plane.  In  a  word,  the  symmetry  is  bilateral,  and  corresponds 

Fig.  22.  Fig.  23.  Fig.  24. 


to  the  type  with  which  we  are  so  familiar  in  the  structure  of 
the  human  body.  This  plan  of  symmetry  is  well  illustrated  by 
Figs.  25,  26,  and  27,  which  represent  the  commonly  occurring 
forms  of  gypsum,  augite,  and  felspar,  three  of  the  most  com- 
mon minerals.  These  figures,  however,  do  not,  like  those  of  the 
previous  sections,  represent  simple  crystalline  forms.  The  crys- 
tals here  represented  are  in  each  case  bounded  by  several  forms, 
and  indeed  in  this  system  such  compound  forms  are  alone  pos- 
sible, for  no  simple  monoclinic  form  can  of  itself  enclose  space. 

Fig.  25.  Fig.  26.  Fig.  27. 


79.  Sixth  or  Triclinic  System.  —  This  system  is  distinguished 
by  an  almost  complete  want  of  symmetry.    Only  opposite  planes 
Fig.  28.  are  similar,  and  two  such  planes  constitute  a 

complete  crystalline  form.  Hence  on  every 
crystal  there  must  be  at  least  three  simple  forms. 
We  may  refer  the  planes  of  any  crystal  to 
three  unequal  axes  all  oblique  to  each  other, 
but  the  position  we  assign  to  them  is  quite  ar- 
bitrary, and  they  have  therefore  little  value  as 
crystallographic  elements.  Fig.  28  represents 
a  crystal  of  sulphate  of  copper,  one  of  the  very  few  subtances 
which  crystallize  in  this  system. 


CRYSTALLINE   FORMS. 


143 


80.  Modifications  on  Crystals.  —  When  several  crystalline 
forms  appear  on  the  same  crystal,  some  one  is  usually  more 
prominent  or  dominant  than  the  rest,  and  gives  to  the  crystal 
its  general  aspect,  the  planes  of  the  secondary  forms  only  ap- 
pearing on  its  edges  or  solid  angles,  which  are  then  said  to  be 
modified  or  replaced.  Thus,  in  Figs.  29,  30,  and  31,  the  solid 
angles  of  a  cube  are  replaced  (or  truncated)  by  the  faces  of  an 
octahedron ;  in  Fig.  32  the  edges  of  the  cube  are  replaced  by 
the  faces  of  the  dodecahedron  ;  in  Fig.  33  the  edges  of  the 
octahedron  are  modified  in  the  same  way  ;  and  in  Fig.  34  the 
solid  angles  of  a  dodecahedron  are  replaced  by  the  faces  of  an 


Fig.  29. 


Fig.  30. 


Fig.  31. 


octahedron.  These  are  all  forms  of  the  isometric  system,  and 
the  relations  of  the  simple  forms  to  each  other,  which  deter- 
mine in  every  case  the  position  of  the  secondary  planes,  will 
be  readily  seen  on  comparing  together  the  figures  already 
given  on  page  138.  These  figures,  like  all  crystallographic 
drawings,  are  geometrical  projections,  and  represent  the  planes 
in  the  same  relative  position  towards  the  crystalline  axes  which 
they  have  on  the  crystal  itself.  Moreover,  since  in  all  figures 
of  crystals  of  this  system  the  axes  are  drawn  in  absolutely 
the  same  position  on  the  plane  of  the  paper,  the  same  face  has 
also  the  same  position  throughout. 

As  a  general  rule,  all  the  similar  parts  of  a  crystal  are 
simultaneously  and  similarly  modified.     This  important  law, 


144 


CRYSTALLINE  FORMS. 


which  is  a  simple  inference  from  the  principles  already  stated, 
is  illustrated   by  the  figures    just  gnren,   and   also    by   Figs. 

Fig.  35.  Fig.  36.  Fig.  37.  Fig.  38. 


35  to  50.     By  carefully  studying  these  figures,  as  well  as  Figs. 
25  to  28  on  page  142,  the  student  will  be  able  to  refer  each  of 

Fig.  39. 

T?J«       Af\ 

Fig.  41. 


Fig.  40. 


the  compound  crystals  here  represented  to  one  or  the  other  of 
the  systems  of  symmetry  already  described,  and  from  this  and 

Fig.  42. _ 

Fig.  43. 

Fig.  44. 


similar  practice  he  will  learn,  better  than  from  any  descrip- 
tions, how  clearly  the  modifications  on  a  crystal  point  out  its 
crystallographic  relations. 


CRYSTALLINE   FORMS. 


145 


81.  Hemihedral  Forms.  —  To  the  law  governing  the  modi- 
fications of  crystals  just  stated,  there  is  one  important  excep- 


Vig.  45. 


Fig.  46. 


Fig.  47. 


Fig.  48. 


tion.     It  not  unfrequently  happens  that  half  the  similar  parts 
of  a  crystal  are  modified  independently  of  the*  other  half.     Thus 


Fig.  49. 


Fig.  50. 


in  Fig.  51  only  one  half  of  the  solid  angles  of  the  cube  are 
truncated.     The  modifying  form  in  this  case  is  the  tetrahedron, 

Fig.  52. 


Fig.  53,  also  a  simple  form  of  the  isometric  system.  When 
all  the  solid  angles  of  the  cube  are  truncated,  the  modifying 
form,  as  has  been  shown,  is  the  octahedron,  and  the  relation 
which  the  tetrahedron  bears  to  the  octahedron  is  shown  by 
Fig.  52.  The  rhombohedron,  Fig.  54,  stands  in  a  similar  re- 
lation to  the  hexagonal  pyramid,  Fig.  55.  From  these  figures- 


146  CRYSTALLINE  FORMS. 

it  is  evident  that  while  the  octahedron  and  the  hexagonal  pyra- 
mid have  all  the  planes  which  perfect  symmetry  requires,  the 

Fig.  55. 


tetrahedron  and  the  rhombohedron  have  only  half  the  number, 
and  in  crystallography  all  forms  which  bear  a  similar  relation 
to  the  forms  of  perfect  symmetry  are  said  to  be  ^e/m'hedral, 
while  the  forms  of  perfect  symmetry  are  distinguished  as  kolo- 
hedral.  The  hemihedral  forms  are  quite  numerous  in  all  the 
systems,  but  with  the  exception  of  the  tetrahedron,  rhombohe- 
dron, and  scalenohedron  (Fig.  17),  they  seldom  appear  except 
as  modifying  planes  on  the  edges  or  solid  angles  of  the  more 
perfect  forms.  As  a  general  rule,  they  are  easily  recognized, 
but  not  unfrequently  they  give  to  a  crystal  the  aspect  of  a  dif- 
ferent system  from  that  to  which  it  really  belongs,  and  may 
lead  to  false  inferences ;  but  these  can,  in  most  cases,  be  cor- 
rected by  a  careful  study  of  the  interfacial  angles. 

82.  Identity  of  Crystalline  Form.  —  As  has  already  been 
stated,  every  substance  is  marked  by  certain  peculiarities  of 
outward  form,  which  are  among  its  most  essential  qualities,  and 
we  must  next  learn  in  what  these  peculiarities  consist.  As  a 
general  rule,  the  same  substance  crystallizes  in  the  same  form, 
but  under  unusual  circumstances  it  frequently  appears  in  other 
forms  of  the  same  system.  Thus  fluorspar  is  usually  found 
crystallized  in  cubes,  but  in  large  collections  crystals  of  this 
mineral  may  be  seen  in  almost  all  the  holohedral  forms  of  the 
isometric  system,  including  their  numerous  combinations.  In 
like  manner  common  salt  usually  crystallizes  in  cubes,  but  out 
of  a  solution  containing  urea  it  frequently  crystallizes  in  octa- 
hedrons. Moreover,  the  same  principle  holds  true  in  regard 
to  substances  crystallizing  in  other  systems,  most  of  whose 
forms  never  appear  except  in  combination.  Thus  the  mineral 


CRYSTALLINE  FORMS.  147 

quartz  generally  shows  the  simple  combination  represented  in 
Fig.  4  ;  but  more  than  one  hundred  other  forms,  all,  however, 
belonging  to  the  same  system,  have  been  observed  on  crystals 
of  this  well-known  substance.  So  also  the  crystals  of  gypsum, 
augite,  and  felspar,  in  most  cases  present  the  forms  already 
figured  on  page  142,  although  other  forms  are  common,  which, 
however,  in  each  case  all  belong  to  the  same  crystalline  system. 
We  never  find  the  same  substance  in  the  forms  of  different  sys- 
tems except  in  those  cases  of  polymorphism  already  described, 
page  135,  where  the  differences  in  other  properties  are  so  great 
that  the  bodies  can  no  longer  be  regarded  as  the  same  substance. 

Among  substances  crystallizing  in  the  isometric  system  the 
crystalline  form  is  not  so  distinctive  a  character  as  it  is  in  other 
cases.  In  this  system  the  relative  dimensions  are  invariable, 
and  the  octahedron,  the  dodecahedron,  and  the  cube,  more  or 
less  modified  by  different  replacements,  are  the  constantly  re- 
curring forms.  Even  here,  however,  specific  differences  may 
at  times  be  found  in  the  fact  that  some  substances  affect  hemi- 
hedral  forms  on  modification,  while  others  do  not.  In  all  the 
other  systems  the  dimensions  of  the  crystal  (the  relative  lengths 
of  its  axes  and  the  values  of  the  interaxial  angles)  distinguish 
each  substance  from  every  other.  But  here,  also,  the  general 
statement  must  be  somewhat  modified. 

We  frequently  find  on  the  crystals  of  the  same  substance 
several  forms  having  different  axial  dimensions.  Thus,  on  the 
crystal  represented  by  Fig.  56,  belonging  to  the  tetragonal 
system,  there  are  three  different  octahedrons,  and  three  cor- 
responding values  of  the  vertical  axis.  But  if,  beginning  with 
the  planes  of  the  octahedron  0,  we  determine 
the  ratio  which  its  vertical  axis  bears  to  the  Flg'  56' 

common  length  of  the  two  lateral  axes,  and 
call  this  value  a,  we  shall  find  that  the  cor- 
responding values  for  the  two  other  octahe- 
drons are  2a  and  £a  respectively.  More- 
over, if  we  extend  our  study  we  shall  also 
find  that  this  example  illustrates  a  general 
principle,  and  that  the  crystalline  forms  of 
a  given  substance  include  not  only  those  of 
identical  axial  dimensions,  but  also  those  whose  dimensions  tear 
to  each  other  some  simple  ratio. 


148  CRYSTALLINE  FORMS. 

This  most  important  law  gives  to  the  science  of  crystallog- 
raphy a  mathematical  basis,  and  enables  us  to  apply  the  exhaus- 
tive methods  of  analytical  geometry  in  discussing  the  various  re- 
lations of  the  subject.  Among  the  actual  forms  of  a  given  sub- 
stance we  fix  on  some  one  as  the  fundamental  form,  and,  taking 
the  values  of  its  axial  dimensions  as  our  standards,  we  are  able 
to  express  the  position  of  the  planes  of  all  the  possible  forms  by 
means  of  very  simple  symbols,  and  also  to  express  by  mathe- 
matical formulae  the  relations  of  the  interfacial  angles  to  the 
same  fundamental  elements  of  the  crystal;  so  that  the  one 
may  readily  be  calculated  from  the  other. 

It  may  seem  at  first  sight  that  the  crystallographic  distinction 
between  different  substances,  insisted  on  above,  is  greatly  ob- 
scured by  the  important  limitations  just  made.  But  it  is  not 
so,  at  least  to  any  great  extent.  The  selection  of  the  funda- 
mental form  of  a  given  substance  is  not  arbitrary,  although  it  is 
based  on  considerations  which  it  lies  beyond  the  scope  of  this 
book  to  discuss.  Moreover,  an  error  in  this  choice  is  not  fun- 
damental, since  the  true  conception  of  the  form  of  a  substance 
includes  not  only  the  fundamental  form,  but  all  those  which  are 
related  to  it.  This  conception,  though  not  readily  embodied  in 
ordinary  language,  is  easily  expressed  by  a  general  mathemat- 
ical formula,  and  is  as  tangible  to  one  familiar  with  the  subject 
as  the  general  statement  first  made. 

But  however  obscure,  to  those  who  are  not  familiar  with 
mathematical  conceptions,  may  be  the  distinction  between  the 
forms  of  different  substances  in  the  same  system,  the  difference 
between  the  different  systems  is  clear  and  definite,  and  it  is 
with  this  broad  distinction  that  we  have  chiefly  to  deal  in  our 
chemical  classification. 

83.  Irregularities  of  Crystals.  —  It  must  not  be  supposed 
that  natural  crystals  have  the  same  perfection  of  form  and 
regularity  of  outline  which  our  figures  might  seem  to  indicate. 
In  addition  to  being  more  or  less  bruised  or  broken  from  acci- 
dental causes,  crystals  are  rarely  terminated  on  all  sides,  —  one 
or  more  of  the  faces  being  obliterated  where  the  crystal  is  im- 
planted on  the  rock,  or  where  it  is  merged  in  other  crystals. 
But  by  far  the  most  remarkable  phase  which  the  irregularities 
of  crystals  present  is  that  shown  by  Figs.  57  to  67.  By  com- 
paring together  the  figures  which  have  been  here  grouped  to- 


CRYSTALLINE  FORMS.  149 

gether  on  the  page,  and  which  represent  in  each  case  different 
phases  of  the  same  crystalline  form,  it  will  be  seen  that  the 
variations  from  the  normal  type  are  caused  by  the  undue  de- 

Fjg.  58. 

rig.  57. 


velopment  of  certain  planes  at  the  expense  of  their  neighbors, 
or  by  an  abnormal  growth  of  the  crystal  in  some  one  direction. 

Fig.  61. 
Fig-  60. 


Such  forms  as  these,  however,  although  great  departures 
from  the  ideal  geometrical  types,  are  in  perfect  harmony  with 

Fig.  62. 

•• 

Fig.  63. 


the  principles  of  crystallography.     The  axis  of  a  crystal  is  not 
a  definite  line,  but  a  definite  direction ;  and  the  face  of  a  crystal 


150 


CRYSTALLINE  FORMS. 


is  not  a  plane  of  definite  size,  but  simply  an  extension  in  two 
definite  directions.  These  directions  are  the  only  fundamental 
elements  of  a  crystalline  form,  and  they  are  preserved  under 


Fig.  64. 


Fig.  66. 


all  conditions,  as  is  proved  by  the  constancy  of  the  interfacial 
angles,  and  of  the  modifications,  on  crystals  of  the  same  sub- 
stance, however  irregular  may  have  been  the  development. 

84.  Twin  Crystals.  —  Every  crystal  appears  to  grow  by  the 
slow  accretion  of  material  around  some  nucleus,  which  is  usually 
a  molecule  or  a  group  of  molecules  of  the  same  substance,  and 
which  we  may  call  the  crystalline  molecule  or  germ.  Now  we 
must  suppose  that  these  molecules  have  the  same  differences  on 
different  sides  which  we  see  in  the  fully  developed  crystal,  and 
which,  for  the  want  of  a  better  term,  we  may  call  polarity.  As 
a  general  rule,  in  the  aggregation  of  the  molecules  a  perfect 
parallelism  of  all  the  similar  parts  is  preserved.  But,  if  molec- 
ular polarity  at  all  resembles  magnetic  polarity,  it  may  well  be 
that  two  crystalline  molecules  might  become  attached  to  each 
other  in  a  reversed  position,  or  in  some  other  definite  position 
determined  by  the  action  of  the  polar  forces.  Assume  now  that 
each  of  these  crystalline  molecules  "  germinates,"  and  the  result 
would  be  such  twin  crystals  as  we  actually  find  in  nature.  The 
result  is  usually  the  same  as  if  a  crystal  of  the  normal  form 
were  cut  in  two  by  a  plane  having  a  definite  position  towards 
the  crystalline  axes,  and  one  part  turned  half  round  on  the 
other ;  and  twins  of  this  kind  are  therefore  called  hemitropes. 
Figs.  68  to  71.  At  other  times  the  germinal  molecules  seem 
to  have  become  attached  with  their  dominant  axes  at  right 
angles  to  each  other,  and  then  there  result  twins  such  as  are 
represented  in  Figs.  72  and  73  ;  and  many  other  modes  of  twin- 


CRYSTALLINE   FORMS. 


151 


ning  are  possible.  Some  substances  are  much  more  prone  to 
the  formation  of  twin  crystals  than  others,  and  the  same  sub- 
stance generally  affects  the  same  mode  of  twinning,  which  may 

Fig.  71. 
Fig.  68.  Fig. 

Fig.  69. 


thus  become  an  important  specific  character.    The  plane  which 
separates  the  two  members  of  a  twin  crystal,  called  the  plane 

Fig.  72. 

Fig.  73. 


of  twinning,  has  always  a  definite  position,  and  is  in  every  case 
parallel  either  to  an  actual  or  to  a  possible  face  on  both  of  the 
two  forms. 

Twin  crystals  always  preserve  the  same  symmetry  of  group- 
ing, and  the  values  of  the  interfacial  angles  between  the  two 
forms  are  constant  on  crystals  of  the  same  substance,  so  that 
they  might  sometimes  be  mistaken  for  simple  crystals  by  un- 
practised observers.  There  is,  however,  a  simple  criterion  by 
which  they  can  be  generally  distinguished.  Simple  crystals 
never  have  re-entering  angles,  and,  whenever  these  occur,  the 
faces  which  subtend  them  must  belong  to  two  individuals. 

The  same  principle  which  leads  to  the  formation  of  twin 
crystals  may  determine  the  grouping  of  several  germinal 
molecules,  and  lead  to  the  formation  of  far  more  complex  com- 


152  CRYSTALLINE  FORMS. 

binations.  Frequently,  as  it  would  seem,  a  large  number  of 
molecules  arrange  themselves  in  a  line  with  their  principal 
axes  parallel  and  their  dissimilar  ends  together,  and  hence  re- 
sult linear  groups  of  crystals  alternating  in  position,  but  so  fused 
into  each  other  as  to  leave  no  evidence  of  the  composite  char- 
acter except  the  re-entering  angles,  and  frequently  these  are 
marked  only  by  the  striations  on  the  surface  of  the  resulting 
faces.  Such  a  structure  is  peculiar  to  certain  minerals,  and 
the  resulting  striation  frequently  serves  as  an  important  means 
of  distinction.  The  orthoclase  and  the  klinoclase  felspars  are 
distinguished  in  this  way. 

85.  Crystalline  Structure.  —  The  crystalline  form  of  a  body 
is  only  one  of  the  manifestations  of  its  crystalline  structure. 
This  also  appears  in  various  physical  properties,  which  are  fre- 
quently of  great  value  in  fixing  the  crystallographic  relations 
of  a  substance,  and  such  is  especially  the  case  when,  on  ac- 
count of  the  imperfection  of  the  crystals,  the  crystalline  form  is 
obscure.  Of  these  physical  qualities  one  of  the  most  impor- 
tant is  cleavage. 

As  a  general  rule,  crystallized  bodies  may  be  split  more  or 
less  readily  in  certain  definite  directions,  called  planes  of  cleav- 
age, which  are  always  parallel  either  to  an  actual  or  to  a  pos- 
sible face  on  the  crystals  of  the  substance,  and  are  thus  inti- 
mately associated  with  its  crystalline  structure.  At  times  the 
cleavage  is  very  easily  obtained,  when  it  is  said  to  be  eminent, 
as  in  the  case  of  mica  or  gypsum,  which  can  readily  be  split 
into  exceedingly  thin  leaves,  while  in  other  cases  it  can  only 
be  effected  by  using  some  sharp  tool  and  applying  considerable 
mechanical  force.  With  a  few  unimportant  exceptions  the 
cleavage  planes  have  the  same  position  on  all  specimens  of  the 
same  substance.  Thus  specimens  of  fluor-spar  may  be  readily 
cleaved  parallel  to  the  faces  of  an  octahedron,  Fig.  5,  those  of 
galena  parallel  to  the  faces  of  a  cube,  Fig.  7,  those  of  blende 
parallel  to  the  faces  of  a  dodecahedron,  Fig.  6,  and  those  of 
calc-spar  parallel  to  the  faces  of  a  rhombohedron,  Fig.  16.  In 
these  cases,  and  in  many  others,  the  cleavage  is  a  more  distinc- 
tive character  than  the  external  form,  and  can  be  more  fre- 
quently observed,  and  we  generally  regard  the  form  produced 
by  the  union  of  the  several  planes  of  cleavage  as  the  funda- 
mental form  of  the  substance. 

Again,  we  always  find  that  cleavage  is  obtained  with  equal 


CRYSTALLINE  FORMS.  153 

ease  or  difficulty  parallel  to  similar  faces,  and  with  unequal 
ease  or  difficulty  parallel  to  dissimilar  faces.  Moreover,  the 
dissimilar  cleavage  faces  thus  obtained  may  generally  be  dis- 
tinguished from  each  other  by  differences  of  lustre,  striation, 
and  other  physical  character ;  and  such  distinctions  are  fre- 
quently a  great  help  in  studying  the  crystallographic  relations 
of  a  substance.  Similar  differences  on  the  natural  faces  of 
crystals  are  also  equally  valuable  guides. 

But,  of  all  the  modes  of  investigating  the  crystalline  structure 
of  a  body,  none  can  compare  in  efficiency  with  the  use  of  polar- 
ized light.  It  is  impossible  to  explain  the  theory  of  this  beau- 
tiful application  of  the  principles  of  optics  without  extending 
this  chapter  to  a  length  wholly  incompatible  with  the  design  of 
this  book.  It  must  suffice  to  say,  that  if  we  examine  with  a 
polarizing  microscope  a  thin  slice  of  any  transparent  crystal  of 
the  second  or  third  system,  cut  perpendicular  to  the  dominant 
axis,  we  see  a  series  of  colored  rings,  intersected  by  a  black 
cross,  and  it  is  evident  that  ^the  circular  form  of  the  rings 
answers  to  the  perfect  symmetry  which  exists  in  these  systems 
around  the  vertical  axis.  If,  however,  we  examine  in  a  similar 
way  a  slice  from  a  crystal  of  one  of  the  last  three  systems,  cut 
in  a  definite  direction,  which  depends  on  the  molecular  structure, 
and  must  be  found  by  trial,  we  see  a  series  of  oval  rings  with 
two  distinct  centres,  indicating  that  the  symmetry  is  of  a  dif- 
ferent type.  Moreover,  the  distribution  of  the  colors  around 
the  two  centres  corresponds  in  each  case  to  the  peculiarities  of 
the  molecular  structure,  and  enables  us  to  decide  to  which  of 
the  three  systems  the  crystal  belongs. 

The  use  of  polarized  light  has  revealed  remarkable  differ- 
ences of  structure  in  different  crystals  of  the  same  substance, 
connected  with  the  hemihedral  modifications  described  above. 
The  Figures  74  and  76  represent  crystals  of  two  varieties  of 
tartaric  acid,  which  only  differ  from  each  other  in  the  position 
of  two  hemihedral  planes,  and  are  so  related  that  when  placed 
before  a  mirror  the  image  of  one  will  be  the  exact  representa- 
tion of  the  other.  The  intermediate  Figure,  75,  represents  the 
same  crystal  without  these  modifications.  Since  the  solid 
angles  are  all  similar,  we  should  expect  to  find  them  all  modi- 
fied simultaneously  ;  but,  while  on  crystals  of  common  tartaric 
acid  only  the  two  front  angles  (as  the  figure  is  drawn)  are  re- 
placed, a  variety  of  this  acid  has  been  discovered  having  simi- 


154 


CRYSTALLINE  FORMS. 


lar  crystals,  whose  back  angles  only  are  modified.  Now,  it  is 
found  that  a  solution  of  the  common  acid  rotates  the  plane  of 
polarization  of  a  beam  of  light  to  the  right,  while  a  similar  so- 


Fig.  74. 


Fig.  75. 


Fig.  76. 


lution  of  this  remarkable  variety  rotates  the  plane  of  polariza- 
tion to  the  left.  This  difference  of  crystalline  structure,  more- 
over, is  associated  with  certain  small  differences  in  the  chemi- 
cal qualities  of  the  two  bodies  ;  but  the  difference  is  so  slight 
that  we  cannot  but  regard  them  as  essentially  the  same  sub- 
stance, and  the  polarized  light  thus  reveals  to  us  the  beginnings 
of  a  difference  of  structure,  which,  when  more  developed,  mani- 
fests itself  in  the  phenomena  of  isomerism.  It  is  a  remarkable 
fact,  worthy  of  notice  in  this  connection,  that  these  two  varieties 
of  tartaric  acid  chemically  combine  with  each  other,  forming  a 
new  substance  called  racemic  acid. 

Questions. 

1.  By  what  peculiar  mode  of  symmetry  may  each  of  the  six  crys- 
talline systems  be  distinguished  ?     How  may  crystals  belonging  to 
the  1st  system  be  recognized  V     How  may  crystals  of  the  2d,  3d, 
and  4th  systems  be  distinguished  by  studying  the  distribution  of 
the  similar  planes  around  their  terminations  or  dominant  axes  ? 
By  what  peculiar  distribution  of  similar  planes  may  the  crystals  of 
the  5th  and  6th  systems  be  distinguished  from  all  others  ?     State 
the  system  to  which  each  of  the  crystals,  represented  by  the  various 
figures  of  this  chapter,  belongs,  and  give  the  reason  of  your  answer 
in  every  case. 

2.  We  find  in  the  mineral  kingdom  two  different  octahedral  forms 
of  titanic  acid  belonging  to  the  tetragonal  system.     In  one  of  these 
forms  the  ratio  of  the  unequal  axes  is  1  :  0.6442,  in  the  other  it  is 
1 :  1.7723.     Can  these  forms  belong  to  the  same  mineral  substance  ? 


CHAPTER  XV. 

ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

86.   General  Principles.  — If  in  a  vessel  of  dilute  sulphuric 
acid  (one  part  of  acid   to  twenty   of  water)  we   suspend   a 
plate  of  zinc  and  a  plate  of  platinum,  opposite  to  each  other, 
and  not  in  contact,  WSTimT'tnat  no  chemical 
action   whatever   takes   place,   provided    the  Fig,  77. 

zinc  and  the  acid  are  perfectly  pure.  As 
soon,  however,  as  the  two  plates  arejinited  by 
a  copper  wire,  as  represented  in  Fig.  77,  chem- 
ical action  immediately  ensues,  and  the  follow- 
ing phenomena  may  be  observed.  Firs£j. 
Bubbles  of  hydrogen  gas  are  evolved  from  the 
surface  of  the  platinum  plate.  Secondly: 
The  zinc  plate  slowly  dissolves,  the  zinc  combining  with  the 
radical  of  the  acid  to  form  zincic  sulphate,  which  is  soluble  in 
water.  Lastly :  A  peculiar  mode  of  atomic  motion  called 
electricity  is  transmitted  through  the  copper  wire,  as  may  be 
made  evident  by  appropriate  means.  If  the  connection  be- 
tween the  plates  is  broken  by  dividing  the  conducting  wire, 
the  chemical  action  instantly  stops,  and  the  current  of  elec- 
tricity ceases  to  flow ;  but,  as  soon  as  the  connection  is  renewed, 
these  phenomena  again  appear. 

Similar  effects  may  be  produced  by  other  combinations  than 
the  one  just  mentioned,  provided  only  certain  conditions  are 
realized.  In  the  first  place,  the  two  plates  must  consist  of 
materials  which  are  unequally  affected  by  the  liquid  contained 
in  the  vessel,  or  cell;  and  the  greater  the  difference  in  this 
respect,  within  manageable  limits,  the  better.  In  the  second 
place,  the  materials,  both  of  plates  and  connector,  must  be  con- 
ductors of  electricity  ;  and,  lastly,  the  liquid  must  contain  some 
substance  for  one  of  whose  radicals  the  material  of  one  of  the 
plates  has  sufficient  affinity  to  determine  its  decomposition  un- 
der the  conditions  present.  Such  a  combination  is  called  a 


156  ELECTRICAL  RELATIONS   OF  THE  ATOMS. 

Voltaic  Cell  The  mode  of  action  of  this  instrument,  which 
since  its  first  discovery  has  been  a  subject  of  controversy,  is 
very  obscure,  but  the  following  theory  gives  an  intelligible  ex- 
planation of  the  general  phenomena,  and  may  serve  a  useful 
purpose  until  greater  certainty  can  be  attained. 

Polarity.  The  phenomena  of  magnetism  have  made  us  familiar  with  a 
condition  of  matter  we  call  polarity,  in  which  bodies  manifest  a  mode  of 
energy  known  as  polar  force.  The  characteristics  of  polar  force  are  as 
follows :  — 

1.  The  energy  is  chiefly  concentrated  at  opposite  points  of  the  polarized  body 
called  its  poles.  2.  The  poles  differ  in  kind  in  so  far  that,  while  unlike  poles 
attract,  like  poles  repel  each  other,  and  while  unlike  poles  neutralize,  like  poles 
enhance  each  the  other's  effect.  3.  With  every  pole  is  always  associated  its  op- 
posite, either  on  the  same  or  a  neighboring  body,  and  in  every  polar  system  the 
sum  *  of  the  polar  energies  of  one  kind  is  exactly  equal  to  that  of  those  of  the 
opposite  kind.  4.  A  polarized  body  induces  a  similar  state  in  ail  neighboring 
bodies  susceptible  of  this  condition,  a  pole  of  a  given  kind  determining  nearest 
to  itself  a  pole  of  the  opposite  kind.  5.  Induction  is  attended  with  no  loss  of 
energy  in  the  inducing  body,  whose  condition  is  frequently  exalted  by  the  reaction 
of  the  induced  polarity.  6.  Polarity  appears  of  different  kinds  as  well  as  in 
different  degrees ;  the  phenomena  of  magnetic,  electrical,  and  chemical  polarity, 
though  similar  in  their  general  features,  differing  widely  in  their  modes  of  man- 
ifestation. 7.  Substances  differ  from  each  other,  not  only  in  their  susceptibility 
to  polarity  of  any  given  kind,  but  also  in  their  power  of  retaining  it.2 

The  study  of  this  class  of  phenomena  has  shown  that  the  energy  man- 
ifested by  polarized  bodies  is  always  the  effect  of  an  attraction  or  repul- 
sion between  poles,  and  that  whenever  they  appear  to  act  on  a  neutral 
body  the  last  is  always  first  polarized  by  induction.  Thus  the  nails 
attracted  by  a  magnet  or  the  straws  attracted  by  an  electrified  stick  of 
sealing-wax  are  all  in  a  polar  condition.  A  horseshoe  magnet,  with 
its  keeper  attached,  affords  a  familiar  illustration  of  these  principles,  which 
will  aid  us  in  explaining  the  more  obscure  phenomena  of  the  Voltaic 
cell.  The  horseshoe  magnet  was  originally  polarized  by  induction,  and 
since  it  is  made  of  hardened  steel  retains  its  magnetism.  The  soft-iron 
keeper  while  in  contact  with  the  magnet  is  as  truly  polarized  as  the  steel. 
It  has  a  north  pole  in  contact  with  the  south  pole,  and  a  south  pole  in 
contact  with  the  north  pole  of  the  magnet.  But  the  moment  it  is  with- 
drawn, all  its  polarity  disappears.  Again,  while  the  magnetic  circuit,  as 
we  call  it,  is  closed,  the  keeper,  by  reacting  on  the  source  of  power,  greatly 
enhances  the  energy  of  the  magnet,  which  will  lift  a  much  greater  weight 
suspended  from  the  keeper  than  it  can  when  the  two  poles  act  separately. 
Fig.  77  a.  Lastly,  if  we  break  a  steel 

magnet,  each  of  the  parts  will 
be  found  to  be  magnetized  with 
Lf.  poles  relatively  situated  as  is 

1  shown  in  Fig.  77  a,  and  since 

-™  this  relation"  of  parts  is  pre- 

1  There  may  be  several  poles  on  the  same  mass  of  matter,  and  the  polarity 
may  be  very  irregularly  distributed.     Such  is  frequently  the  condition  of  the 
lode-stone  or  of  a  steel  bar  irregularly  magnetized. 

2  For  example,  the  metals  iron,  nickel,  and  cobalt,  with  a  few  of  their  com- 
pounds, are  the  only  substances  susceptible  of  magnetic  polarity  to  a  high 
degree.     Again,  a  hardened  steel  bar  retains  the  polar  condition  more  or  less 
permanently  as  in  the  common  magnet,  but  soft  iron  loses  its  magnetic  virtue 
the  moment  the  inducing  cause  ceases  to  act. 


ELECTRICAL  RELATIONS  OF   THE  ATOMS.  157 

served,  however  far  we  may  carry  the  subdivision,  we  are  led  to  the  conclu- 
sion that  the  polarity  is  a  Fi    77  6 


molecules  of  which  it  con- 
gists,  and  picture  to  our- 
selves  as  the  condition  of  a 
magnetized  bar  that  which 
is  rudely  represented  in  Fig.  77  6. 

Theory  of  Chemical  Polarity.  As  the  molecules  of  iron  may  be  mag- 
netically polarized,  we  infer  that  the  molecules  of  all  substances  are  sus- 
ceptible of  different  polar  states,  and  we  conceive  that  chejjusjnJLJ.S  ft 
manifestation  of  a  molecular  condition,  which  we  may  distinguish  as 
chemical  polarity.  It  must  be  remembered,  however,  that  we  do  not  un- 
derstand the  cause  of  the  differences  in  the  various  modes  of  polar  energy; 
and  in  saying  that  the  molecules  of  matter  may  be^chemically  polarized, 
we  mean  merely  that  they  are  susceptible  of  a  condition  whose  general 
features  have  been  indicated  above.  Our  theory  further  assumes  that 
with  some  molecules  the  polarity  is  inherent  and  therefore  permanent, 
while  with  others  it  can  only  be  .induced  by  extraneous  causes.  These 
last,  however,  may  become  polarized  by  induction  to  as  high  or  even  a 
higher  degree  than  the  first,  but  the  condition,  like  that  of  an  electro- 
magnet, is  transient,  varying  with  the  inducing  eause.  Again,  as  every 
analogy  would  lead  us  to  believe,  our  theory  further  assumes  that  different 
substances  are  susceptible  of  chemical  polarity  (whether  it  be  inherent  or 
assumed)  to  very  different  degrees,,  and  that  the  susceptibility  varies  un- 
der different  conditions.  Lastly,  our  theory  supposes  that  the  chemical 
activity  of  a  substance  depends  on  the  degree  of  polarity  inherent  in  its 
molecules,  and  it  refers  the  well-known  active  qualities  of  acids  and 
alkalies  to  the  fact  that  their  peculiar  constitution  renders  their  molecules 
strongly  polarized,  while  the  inert  qualities  of  most  of  the  elementary 
substances  is  explained  by  the  neutral  condition  which  their  homogeneous 
structures  would  naturally  produce  in  their  molecules.  Thus,  for  exam- 
ple, we  suppose  that  every  molecule  of  sulphuric  acid,  H^SO^  or  of  hy- 
drochloric acid,  H-Cl,  or  of  sodtc  hydrate,  H-NaO,  is  naturally  polarized, 
while  on  the  other  hand  the  molecules  of  zinc,  Zn,  of  magnesium,  Mg, 
of  hydrogen,  H~H,  and  of  oxygen,  0=0,  are  all  normally  neutral.  As 
soon,  however,  as  we  place  zinc  in  contact  with  dilute  sulphuric  acid, 
the  metallic  molecules  become  polarized  by  induction  to  the  degree  of 
which  they  are  susceptible  under  the  influence  of  this  acid.  A  powerful 
attraction  is  thus  developed  and  a  familiar  chemical  change  is  the  result. 
If  magnesium  is  treated  in  a  similar  way,  the  action  is  more  energetic, 
because,  as  we  suppose,  the  molecules  of  this  metal  are  susceptible  of  u 
higher  degree  of  polarity,  and  the  force  developed  is  therefore  proportion- 
ally stronger.  On  the  other  hand,  with  metallic  copper  there  is  no  action 
under  the  same  conditions,  because  the  molecules  of  the  metal  do  not  ac- 
quire a  sufficient  degree  of  polarity  to  determine  chemical  change. 

While,  however,  the  molecular  structure  appears  to  be  the  most  impor- 
tant, it  is  evidently  by  no  means  the  only  cause  which  determines  chemical 
polarity.  The  highly  active  qualities  of  the  alkaline  metals  and  of  the 
chlorine  group  of  elementary  substances  indicate  that  their  molecules, 
although  apparently  homogeneous  in  structure,  must  be  permanently 
polarized.  Moreover,  the  fact  that  a  high  degree  of  energy  is  developed 
in  many  of  the  elementary  substances,  as  in  oxygen  gas,  by  a  simple  ele- 
vation of  temperature,  and  the  general  principle  that  heat  hastens  chem- 

1  This  term  is  synonymous  with  the  old  term  chemical  affinity,  to  which  it 
is  on  many  accounts  to  be  preferred. 


158      ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

ical  changes,. seem  to  indicate  that  the  polar  condition  may  be  frequently 
produced .  by  this  agent  alone.  So  also  the  process  of  photography  is 
most  simply  explained  by  the  theory  that  the  sun's  rays  excite  a  similar 
condition  in  the  silver  compouncis  on  the  surface  of  the  sensitive  plate, 
and  the  effect  of  continuous  electrical  discharges  in  converting  oxygen 
gas  into  that  peculiar  active  modification  of  this  substance  called  ozone, 
may  be  regarded  as  a  direct  result  of  their  polarizing  power. 

Theory  of  Electricity.  The  study  of  the  phenomena  of  optics  has  led 
physicists  to  the  conclusion  that  there  exists  throughout  space,  filling  not 
only  the  interplanetary  but  also  the  intermolecular  spaces,  a  highly  atten- 
uated but  at  the  same  time  wonderfully  elastic  medium  which  is  called 
the  ether  (92)X  Again,  the  phenomena  of  heat  indicate  that  the  molec- 
ular forces  have  an  energy  which  is  adequate  to  cope  with  this  very  great 
elasticity ;  and  we  can  conceive  that  they  condense  around  these  molecules 
greater  or  less  quantities  of  this  ether,  thus  giving  to  each  a  distinct  at- 
mosphere, but  one  which  merges  into  that  unrversally  diffused  medium 
in  which  molecule  and  planet  alike  float.  Now  our  theory  supposes  that 
electrical  phenomena  are  caused  by  disturbances  in  the  composition  of 
these  ethereal  atmospheres.  The  electrical  ether,1  as  we  assume,  consists  of 
two  separable  materials,  which,  adopting  names  long  used  in  science,  we 
will  call  positive  and  -negative  or  vitreous  and  resinous  electricities.  In 
all  the  terrestrial  region  of  the  solar  system  at  least  these  electricities  are 
blended  in  certain  definite  proportions,  like  the  constituents  of  the  earth's 
atmosphere,  but  by  various  causes  they  may  become  separated  and  more 
or  less  isolated  either  on  the  same  or  on  different  molecules.  Whenever 
this  takes  place,  the  two  electricities  tend  to  flow  together  until  the  nor- 
mal condition  is  restored  in  accordance  with  the  law  of  diffusion ;  but  the 
force  of  diffusion  in  these  molecular  atmospheres  is  vastly  greater  and 
the  process  vastly  more  rapid  than  it  is  in  the  terrestrial  atmosphere,  be- 
cause the  elasticity  of  the  ether  so  greatly  exceeds  that  of  the  air.  This 
being  granted,  our  theory  further  supposes  that  every  process  of  electrical 
excitement  causes  a  separation  of  the  constituents  of  the  ether,  and  that 
an  electrified  body  is  one  on  whose  molecules  one  or  the  other  of  the  two 
electricities  is  to  a  greater  or  less  degree  isolated  ;  and  again,  that  the  fa- 
miliar phenomena  of  attraction  and  repulsion  between  electrified  bodies  are 
the  effects  of  pressure  caused  by  the  diffusive  force  ;  and  lastly,  that  an 
electrical  current  consists  in  an  actual  transfer  of  the  ethereal  material 
between  the  molecules  of  the  conductor.  We  have  not  space,  however, 
to  follow  out  the  theory  into  its  mechanical  details,  and  we  must  content 
ourselves  with  applying  it  to  the  explanation  of  the  phenomena  of  the 
Voltaic  cell. 

Theory  of  Voltaic  Cell.  In  studying  chemical  reactions  we  have  thus 
far  overlooked  the  molecular  atmospheres  ;  but  it  is  evident  that,  if 
the  above  theory  is  correct,  they  must  enter  as  important  factors  into 
every  chemical  change.  This  theory  assumes  that 'the  condition  of  the 
atmosphere  is  intimately  connected  with  that  of  the  molecule,  although 
in  what  way  it  does  not  attempt  to  explain.  When  the  molecule  is  polar- 
ized, the  two  electricities  are  more  or  less  fully  separated  and  isolated 
around  the  molecular  poles  ;  and  if  the  polarity  is  inherent  this  condition 
is  permanent.  If,  however,  the  polar  state  is  induced,  the  neutral  condi- 
tion is  restored  as  soon  as  the  inducing  force  ceases  to  act.  Let  us  study 
now  frcm  this  new  point  of  view  the  familiar  reaction  of  sulphuric  acid 
on  zinc  referred  to  above. 

Zii  +  (HzSOt  -f-  Aq)  =  (ZnSOt  +  Ag)  +  SMS. 

1  As  it  is  not  important  for  our  present  purpose  to  inquire  whether  the  elec- 
trical ether  is  identical  or  only  is  mingled  with  the  luminiferous  ether,  this 
question  is  here  left  in  abeyance. 


ELECTRICAL  RELATIONS   OF  THE   ATOMS.  159 

The  molecule  HASO^  is  inherently  polarized  and  induces  at  once  a 
similar  condition  in  the  normally  neutral  molecule ^Zn.  At  the  poles  of 
each  of  these  molecules  we  have  therefore  free  electricity.  When  now  Zn 
replaces  7/2  in  H2S04  it  takes  with  it  into  its  new  combination  only  free 
positive  electricity,  leaving  behind  the  corresponding  negative  electricity 
on  the  adja-ent  molecule  of  zinc.  Meanwhile  the  hydrogen  atoms  thus 
liberated  bring  with  them  to  form  the  molecule  H-H  only  positive  elec- 
tricity. We  have  thus  set  free  on  opposite  molecules  at  the  same  time 
equivalent  quantities  of  the  two  electricities,  and  the  equilibrium  being 
thus  disturbed,  an  interchange  at  once  takes  place  between  them,  by 
which  the  normal  condition  of  their  atmospheres  is  restored.  In  order 
to  make  this  point  clearer,  we  have  endeavored  to  illustrate  the  reaction  in 
the  following  diagram  :  — 

HfSOi  Zn  Zn 

'    Factors     M      || 

^|      IP         ^ir  ^IIP7 

^ — JP" 

H-H  Zn^SOi  Zn 

Products  if  Til  Jill 


This  diagram,  however,  indicates  very  imperfectly  the  conception  we 
have  formed  of  the  process,  and  there  are  certain  quantitative  relations 
between  the  parts  which  must  not  be  overlooked,  although  they  can  be 
as  yet  but  very  imperfectly  understood.  We  should  naturally  infer  that 
the  quantity  of  ethereal  atmosphere  would  be  determined  in  every  case  by 
the  mass  of  the  molecule,  but  the  quantities  of  free  electricities  separated 
from  this  'atmosphere  under  different  conditions  seem  to  depend  on  the 
atomicities  of  the  radicals  of  which  the  molecule  consists.  At  least,  the 
facts  indicate  that  the  amount  offree  electricity  which  any  group  of 
atoms  takes  out  of  the, molecule  from  which  it  is  parted  is  exactly  meas- 
ured by  the  number  of  atomic  bonds  thus  broken.  Hence  in  our  diagram 
the  amount  of  positive  electricity  which  H^  takes  from  H^SO^  is  a  defr- 
nite  quantity  and  exactly  equal  to  that  'which  Zn  carries  in  to  take  its 
place.  Moreover,  this  last  quantity  came  originally,  not  from  one,  but 
from  two  zinc  molecules,  and  the  chemical  metathesis  between  Hz  and 

J£n  was  accompanied  by  an  interchange  of  electricities  between  the  zinc 
molecules,  by  which  all  the  free  positive  electricity  passed  to  the  one 
which  entered  into  combination,  and  all  the  free  negative  electricity  to 
the  one  left  behind  ;  and  further,  as  already  stated,  this  free  negative  elec- 
tricity is  equivalent  to  the  free  positive  electricity  on  the  hydrogen  mole- 
cule formea  at  the  same  time. 

If,  as  in  the  usual  form  of  the  reaction  we  have  been  studying,  the  acid 
sufficiently  diluted  is  poured  upon  clippings  of  sheet  zinc,  it  is  found  that, 
although  the  mass  of  the  metal  is  polarized  throughout,  the  polarity  is 
very  irregularly  distributed.  A  multitude  of  negative  polar  points  are 
formed  upon  the  surface,  from  which  bubbles  of  hydrogen  gas  are  evolved, 
and  around  these  are  spaces  positively  polarized*  WfieTe  the  metal  enters 
into  solution.  According  to  our  theory,  when  the  molecules  of  metal  re- 
place the  atoms  of  hydrogen  they  take  with  them  positive  electrical 
charges,  leaving  behind  equivalent  negative  charges,  and  these  are  trans- 

'initted  from  molecule  to  molecule  of  the  metal,  until  they  reach  one  of 
the  negative  polar  points  above  mentioned.  It  is  there  that  the  inter- 
change takes  place  with  the  positive  charges  on  the  molecules  of  hydro- 
gen gas  as  rapidily  as  these  are  formed.  The  polar  points  just  referred 
to  appear  to  be  determined  by  variations  of  texture  or  bits  of  impurity 


160     ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

in  the  metal,  and  this  is  the  reason  that  the_£en.eral  polarity  of  the  mass 
is  so  irregularly  distributed.  If  the  metal  is  absolutely  pure  and  uni- 
form in  texture,  or  if  the  surface  of  the  common  sheet  zinc  is  previously 
amalgamated,  there  is  no  local  action,  and  the  zinc  will  not  dissolve  unless 
we  fasten  to  the  metal  a  piece  of  some  material  less  readily  acted  on  by 
the  acid,  which  must  be  also  a  conductor  of  electricity.  But  when  this  is 
done,  the  whole  mass  becomes  polarized  uniformly  throughout,  after  the 
pattern  represented  in  Fig.  77  b.  Of  this  system  the  surface  of  the  zinc 
forms  the  positive  pole,  and  the  surface  of 'the  second  material  the  nega- 
tive pole.  Chemical  action  ensues  as  before,  and  while  zinc  dissolves  at 
the  positive  pole,  hydrogen  gas  is  evolved  from  the  negative  pole. 

We  are  now  prepared  to  understand  the  conditions  in  the  Voltaic  cell 
represented  in  Fig.  77.  Here  we  have  a  plate  of  zinc  and  a  plate  of  pla- 
tinum, united  by  a  metallic  wire  and  dipping  together  into  the  acid  liquid, 
with  their  surfaces  opposed  to  each  other  and  not  touching.  Here,  also, 
the  two  plates  with  the  conductor  form  one  uniformly  polarized  system, 
of  which  the  surface  of  the  zinc  is  the  positive  and  the  surface  of  the  pla- 
tinum the  negative  pole.  The  polarity  of  this  arrangement  is  induced 
by  the  action  of  the  acid,  whose  molecules  are  inherently  polarized. 
Moreover,  under  these  conditions  the  mass  oTacicT  oe- 
Fig-  78.  tween  the  plates  forms  also  a  uniformly  polarized 

system,  the  molecules  arranging  themselves  in  polar 
lines  as  represented  in  Fig  78.  We  may  compare 
the  combination  thus  formed  to  a  magnetic  circuit, 
consisting  of  a  horseshoe  magnet  and  its  armature, 
or  rather  of  a  bar  magnet  with  a  horseshoe  armature. 
The  inherently  polarized  liquid  corresponds  to  the 
permanent  magnet,  the  system  of  metallic  plates  to 
the  armature  with  its'induced  polarity.  Now  just  as  in  the  magnetic  cir- 
cuit we  have  a  strong  attractive  force"  at  the  surfaces  where  the  armature 
touches  the  magnet,  so  in  the  Voltaic  circuit  we  have  a  powerful^  force 
exerted  at  each  of  the  corresponding  surfaces.  A  mutmu  attraction  is 
exerted  between  the  hydrogen  end  of  the  acid  molecule  and  the  platinum 
surface  on  one  side,  and  the  sulphion  end x  of  the  same  molecules  and 
the  zinc  surface  on  the  other  side.  These  forces  are  adequate  to  decom- 
pose the  acid.  The  sulphion  atoms  enter  into  union  with  the  zinc 
to  form  zincic  sulphate,  which  dissolves  in  the  acid  liquid,  while  the  hy- 
drogen atoms  combine  with  each  other  to  form  molecules  of  hydrogen 
gas,  which  collects  in  bubbles  that  rise  along  the  surface  of  the  platinum 
plate.  Meanwhile,  every  molecule  of  zinc  which  enters  into  solution 
leaves  behind 'a  charge  of  negative  electricity,  and  every  molecule  of  hy- 
drogen gas  carries  to  the  surface  of  the  platinum  plate  a  charge  of  posi- 
tive electricity,  and  these  opposite  charges  flow  together  through  the  con- 
ductor, forming  what  we  call  an  electrical  current,  which  tends  to  restore 
the  electrical  equilibrium  that  the  chemical  action  destroys. 

Electrical  Current.  According  to  our  theory  an  electrical  current  con- 
sists in  the  last  analysis  in  the  transfer  of  the  ethereal  medium  between 
neighboring  molecules,  the  one  giving  up  a  quantity  of  positive  electricity 
SffdTeceiving  an  equivalent  portion  of  negative  electricity  in  its  stead.  This 
transfer  is  supposed  to  take  place  at  the  surface  of  contact  between  the  molec- 
ular atmospheres  by  a  process  similar  to  diffusion  (58),  and  implies  an 
oscillation  of  the  molecules  by  which  each  is  brought  alternately  in  near 
proximity  to  its  neighbors  on  either  side.  The  oscillatory  motion  is 
maintained  by  the  alternate  attractions  and  repulsions,  which  the  varying 
phases  of  the  molecules  necessarily  determine,  and  is  a  most  important 

l  For  the  sake  of  simplicity  we  have  represented  in  the  figures  molecules 
of  H-Cl  instead  of  SfSO^  but  the  theory  applies  equally  to  both. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.  161 

element  of  the  electrical  current.  It  can  easily  be  imitated  by  suspending 
with  silk  threads  small  metallic  balls  between  two  brass  knobs  connected 
with  the  conductors  of  an  electrical  machine,  so  that  they  hang  near  but 
at  equally  small  distances  from  each  other  on  the  same  line.  The  continu- 
ous oscillation  of  these  balls,  while  the  machine  is  in  action,  illustrates  what 
we  conceive  to  be  the  mode  of  motion  in  the  molecules  of  a  conductor. 

If  the  above  explanation  is  correct,  it  is  obvious  that  an  electrical  cur- 
rent in  a  solid  conductor  has  two  distinct  elements :  first,  an  oscillatory 
motion  of  the  molecules;  secondly,  a  mutual  transfer  of  the  two  modifica- 
tions  of  the  electrical  ether  from  molecule  to  molecule,  along  the  lirfes'TrYrlt- 
ing  the  opposite  poles  of  the  polar  system,  which  every  current  implies. 
But  in  the  acid  liquid,  which  not  only  originates  the  current  but,  also 
forms  a  part  of  the  circuit,  the  relations  are  somewhat  different.  There 
the  transfer  of  the  two  electricities  is  attended  with  a  decomposition  of  the 
acid  molecules,  and  the  opposed  atoms,  each  bearing'  its  charge  of  elec- 
tricity, actually  travel  from  one  plate  to  the  other.  Thus  we  have  the 
singular  phenomenon  produced  of  two  coexisting  atomic  currents  through- 
out the  mass  of  the  liquid,  a  stream  of  sulphion  atoms  constantly  setting 
towards  the  zinc  plate,  and  a  stream  of  hydrogen  atoms  flowing  in  vthe 
opposite  direction  in  the  same  space  towards  the  platinum  plate.  The 
result  is  produced  by  a  constant  metathesis  along  the  whole  line  of  mole- 
cules between  the  two  plates,  so  that  for  every  atom  of  sulphion  which 
enters  into  union  with  the  zinc  a  double  atom  or  molecule  of  hydrogen 
is  set  free  at  the  face  of  the  platinum  plate. 

As  our  theory  shows,  the  opposite  currents  of  atoms  in  the  liquid  and 
the  opposite  currents  of  electricity  in  the  solid  conductor  are  mutually 
dependent.  Hence,  if  the  connection  is  broken  so  that  the  motion  can 
no  longer  be  transmitted  through  the  conductor,  the  motion  in  the  liquid 
itself  ceases ;  and  if  by  any  means  the  motion  through  the  conductor  is 
checked  the  motion  of  the  atoms  in  the  liquid  is  reduced  to  the  same  ex- 
tent. The  two  currents,  which,  as  we  have  seen,  are  continuous  through- 
out the  whole  circuit,  take  the  names  of  the  two  kinds  of  electricity  which 
they  respectively  carry  ;  that  flowing  into  the  conducting  wire  from  the 
platinum,  or  inactive  plate,  being  called  the  positive  current,  and  that 
from  the  zinc,  or  active  plate,  the  negative  current.  Reasoning  from  cer-. 
tain  mechanical  phenomena,  the  physicists  originally  concluded  that  the 
electrical  current  flowed  in  but  one  direction,  that  is,  through  the  con- 
ducting wire  from  the  platinum  plate  to  the  zinc,  and  from  the  zinc  plate 
through  the  liqiiid  back  again  to  the  platinum ;  and  now,  when  the  direc- 
tion of  the  current  is  spoken  of,  it  is  this  direction,  that  of  the  positive 
current,  which  is  always  meant. 

87.  Electrical  Conducting  Power  or  Resistance. —  Different 
materials  transmit  the  electric  current  with  very  different  de- 
grees of  facility  ;  for  while  in  some  this  peculiar  form  of  mol£O 
ular  motion  is  easily  maintained,  in  others  the  molecules  yield 
to  it  only  with  difficulty,  and  many  substances  seem  not  to  be 
susceptible  of  it.  The  conducting  powers  of  different  metallic 
wires  have  been  very  carefully  studied,  and  some  of  the  most 
trustworthy  results  are  collected  in  the  following  table.  Silver 
is  the  best  conductor  known,  and,  assuming  that  a  silver  wire  of 
definite  size  and  100  centimetres  long  is  taken  as  the  standard, 
the  number  opposite  the  name  of  each  metal  is  the  length  in 
centimetres  of  a  wire  made  of  this  metal,  arid  of  the  same  siz.e 
11 


162 


ELECTRICAL  RELATIONS  OF  THE  ATOMS. 


as  the  first,  which  will  oppose  the  same  resistance  to  the  trans- 
mission of  the  current.  The  second  column  gives  the  relative 
resistances  of  wires  of  the  same  materials  when  of  equal  size 
and  of  equal  lengths.  The  relative  or  specific  resistances  of  two 
such  wires  must  evidently  be  inversely  proportional  to  their 
conducting  powers,  and  thus  the  "numbers  of  the  second  column 
are  easily  calculated  from  those  of  the  first.  For  the  results 
collated  in  this  table  we  are  indebted  to  the  careful  investiga- 
tions of  Professor  Matthiessen. 


Pure  Metals. 

Conducting  Power. 

Specific  Resistance. 

Silver 

(hard  drawn) 

At  0°.            At  100°. 

100.00         71.56 

At  0°.            At  100°. 

1.000         1.397 

Copper 

(hard  drawn) 

99.95         70.27 

1.0005       1.423 

Gold 

(hard  drawn) 

77.96         55.90 

1.283         1.788 

Zinc 

29.02         20.67 

3.445         4.838 

Cadmium 

23.72         16.77 

4.216          5.964 

Cobalt 

17.22 

5.808 

Iron 

(hard  drai 

m) 

16.81 

5.948 

Nickel 

13.11 

7.628 

Tin 

12.36           8.67 

8.091       11.53 

Thallium 

9.16 

10.92 

Lead 

8.32           5.86 

12.02         17.06 

Arsenic 

4.76           3.33 

21.01          30.03 

Antimony 

4.62           3.26 

21.65         30.68 

Bismuth 

1.245         0.878 

80.34       113.9 

Commercial 
.  Metals. 

C.P. 

Sp.  R. 

(P. 

Commercial 
Metals. 

C.  P. 

Sp.  R. 

GO. 

Copper 

77.43 

1.291 

18.8 

Iron 

14.44 

6.924 

20.4 

Sodium 

37.43 

2.672 

21.7 

Palladium 

12.64 

7.911 

17.2 

Aluminum 

33.76 

2.962 

19.5 

Platinum 

10.53 

9.497 

20.7 

Magnesium 

25.47 

3.926 

17.0 

Strontium 

6.71 

14.90 

20.5 

Calcium 

22.14 

4.516 

16.8 

Mercury 

1.63 

61.35 

22.8 

Potassium 

20.85 

4.795  20.4 

Tellurium 

0.00077 

129,800 

19.6 

Lithium 

19.00 

.5.262 

20.0 

Red  Phosphorus 

0.00000123 

81,300,00024.0 

If,  next,  we  compare  wires  of  the  same  material,  but  of  dif- 
ferent sizes,  we  find  that  the  resistance  increases  as  the  length, 
and  diminishes  as  the  area,  of  the  section.  Moreover,  if  we 
adopt  some  absolute  standard  of  resistance,  like  that  selected  by 
the  English  physicists,  we  can  easily  express  the  resistance  of 
any  given  conductor  in  terms  of  this  unit.  It  must  be  remem- 
bered, however,  in  making  such  comparisons,  that  the  resist- 
ance varies  with  the  temperature,  and  also  that  the  conducting 
power  of  the  same  metal  is  materially  influenced  both  by  its 
physical  condition  and  by  the  presence  of  impurities. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.      163 

88.  Ohm's  Law.  —  The  first  effect  of  the  chemical  forces  in 
the  cell  of  an  electrical  combination  is  to  marshal  the  dissimilar 
atoms  of  the  active  liquid  between  the  plates  into  lines,  which 
at  once  begin  to  move  in  parallel  columns,  but  in  opposite  di- 
rections (Fig.  78).  MoreoverTeach  one  of  these  lines  of  moving 
atoms  is  continued  by  a  corresponding  line  of  oscillating  atoms 
in  the  conducting  wire,  and  thus  is  formed  a  continuous  circuit 
returning  upon  itself.  The  union  of  all  the  lines  of  force  in 
the  two  opposite  coexisting  streams  constitutes  in  any  case  the 
electrical  current,  and  the  different  parts  of  this  continuous  chain 
are  so  related  that  the  total  amount  of  motion  is  always  the  same 
at  every  point  on  the  circuit,  and  no  more  lines  of  moving  atoms 
form  in  the  liquid  between  the  plates  than  can  be  continued 
through  the  oscillating  atoms  of  the  solid  conductors. 

If  we  adopt  this  theory,  it  is  obvious  that  the  strength  of  any 
electrical  current  must  depend,  —  first,  on  the  number  of  con- 
tinuous lines  of  force,  and  secondly,  on  the  strength  of  the 
polarity  transmitted  through  each  of  these  channels.  Of  these 
two  elements,  the  first  is  determined  solely  by  the  total  resist- 
ance which  the  various  parts  of  the  circuit  oppose  to  the  elec- 
trical motion,  and  the  greater  this  resistance  the  less  will  be 
the  number  of  the  lines  of  force.  The  second  element  is  de- 
termined by  the  value  of  the  resultants  of  all  the  polar  forces 
acting  in  any  combination,  which  draw  the  dissimilar  atoms 
towards  the  opposite  plates,  —  a  value  which  depends  solely  on 
the  chemical  relations  of  the  materials  of  the  plates  to  that  of  the 
active  liquid,  and  is  what  is  called  the  electromotive  force  of  the 
combination,  a  quantity  we  will  represent  by  E. 

It  appears,  then,  from  the  above  analysis,  that  an  electrical 
current  is  a  continuous  chain,  which  is  sustained  in  a  regulated 
and  equable  motion  in  all  its  parts  by  the  chemical  activity  in 
the  cell,  and  that  the  strength  of  this  current  at  any  point  of  the 
chain  must  be  directly  proportional  to  the  electromotive  force, 
and  inversely  proportional  to  the  sum  of  the  resistances  through- 
out the  circuit.  If,  then,  we  represent  the  resistance  in  the  con- 
ducting wire  by  r,  the  resistance  of  the  liquid  between  the  plates 
of  the  cell  by  7?,1  and  also  the  strength  of  the  current  by  <7,  we 
shall  have,  in  every  case, 

[62] 


The  resistance  of  any  circuit  may  be  conveniently  divided  into  two  parts, 


164      ELECTKICAL  RELATIONS  OF  THE  ATOMS. 

The  quantities  (7,  J?,  r,  and  E  may  all  be  accurately  measured, 
and  stand  in  each  case  for  a  certain  number  of  arbitrary  units, 
whose  relations  will  hereafter  be  stated. 

89.  Electromotive  Force  and  Strength  of  Current.  —  It  would 
seem  at  first  sight  as  if  the  strength  of  an  electric  current  might 
be  increased  by  simply  enlarging  the  size  of  the  plates  in  the 
combination  employed,  and  obviously  the  number  of  possible 
lines  of  moving  atoms  which  could  be  marshalled  in  the  liquid 
between  the  plates  would  thus  be  increased ;  but,  as  has  been 
stated,  the  parts  of  the  circuit  are  so  intimately  connected  that 
no  greater  number  of  lines  of  atoms  can  form  between  the  plates 
than  can  be  continued  through  the  whole  circuit,  and  practically 
there  may  be  formed  between  the  smallest  plates  a  vastly  greater 
number  of  atomic  lines  than  can  be  continued  through  any  con- 
ductor, however  good  its  quality  or  however  ample  its  size. 
Hence  it  is,  that  by  increasing  the  size  of  the  plates  we  mul- 
tiply the  lines  of  force  only  in  so  far  as  we  thereby  lessen  the 
resistance  in  the  liquid  part  of  the  circuit.  We  thus  simply 
lessen  the  value  of  R  in  Ohm's  formula  [62]  ;  but  if  this  value 
is  already  small  as  compared  with  r,  that  is,  if  the  resistance  in 
the  cell  is  small  compared  with  that  in  the  conductor,  no  mate" 
rial  gain  in  the  power  of  the  current,  or  in  the  value  of  (7,  will 
result.  On  the  other  hand,  if  the  exterior  resistance,  r,  is  small, 
or  nearly  nothing,  as  when  the  plates  are  connected  by  a  thick 
metallic  conductor,  then  the  value  of  C  will  increase  in  very 
nearly  the  same  proportion  as  the  size  of  the  plates  is  enlarged, 
and  the  value  of  JR,  in  consequence,  diminished.  Under  these 
conditions,  the  number  of  lines  of  moving  atoms  is  greatly  mul- 
tiplied, and  we  obtain  a  current  of  very  great  volume,  but  only 
flowing  with  the  limited  force  which  the  single  cell  is  capable 
of  maintaining.  Such  a  current  has  but  little  power  of  over- 
coming obstacles ;  and  if  we  attempt  to  condense  it  by  using  a 
smaller  conductor,  we  reduce,  as  has  been  said,  the  chemical 
action  which  keeps  the  whole  in  motion,  and  thus  lessen  the 
volume  of  the  flow.  This  is  generally  expressed  by  saying 

first,  the  resistance  of  the  conducting  wire,  and  secondly,  the  resistance  of  the 
liquid  portion  of  the  circuit  between  the  two  plates  of  the  cell.  The  resistance 
01  the  solid  conductor  may  be  readily  estimated  on  the  principles  stated  in  the 
last  section,  and  the  resistance  of  liquid  may  be  measured  in  a  similar  way. 
The  last  depends,  —  1.  On  the  conducting  power  of  the  liquid ;  2.  On  the  length 
of  the  liquid  circuit,  which  is  determined  by  the  distance  apart  of  the  plates  ; 
8.  On  the  area  of  the  section  of  the  liquid  conductor,  which  is  determined  by 
the  size  of  the  plates;  and,  4.  On  the  temperature. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.  165 

that  the  current  has  large  quantity,  but  small  intensity,  or  more 
properly,  electromotive  power. 

It  must  now  be  obvious  from  the  theory,  that  we  cannot  in- 
crease effectively  the  intensity  of  a  current  (its  power  of  over- 
coming obstacles)  without  in  some  way  increasing  the  chemical 
activity,  or,  in  other  words,  the  electro-motive  force  of  the  com- 
bination employed,  and  Ohm's  formula  leads  to  the  same  result. 
If  the  value  of  r  in  our  formula  is  very  large  as  compared 
with  R,  we  cannot  increase  it  still  farther  without  lessening  the 
total  value,  <7,  unless  at  the  same  time  we  increase  the  value 
of  E.  Now,  this  electro-motive  force  may  be,  to  a  certain  ex- 
tent, increased  by  using  a  more  active  combination ;  but  the 
limit  in  this  direction  is  soon  reached,  and  the  construction  of 
the  cell  which  has  been  found  practically  to  be  the  most  effi- 
cient will  be  described  below. 

We  can,  however,  increase  the  effective  electro-motive  force 
to  almost  any  extent  by  using  a  number  of  cells,  and  coupling 
them  together  in  the  manner  represented  by  Fig.  79,  the  plati- 
num plate  of  the  first  cell  being  united  by  a  large  metallic  con- 
nector to  the  zinc  plate  of  the  second,  and  so  on  through  the 
line,  until  finally  the  external  conductor  establishes  a  connec- 
tion between  the  platinum  plate  of  the  last  cell  and  the  zinc 
plate  of  the  first.  Such  a  combination  as  this  is  called  a  Gal- 
vanic or  Voltaic  *  battery,  and  the  current  which  flows  through 
such  a  combination  has  a  vastly  greater  power  of  overcoming 
resistance  than  that  of  any  single  cell,  however  large. 

The  increased  effect  obtained  with  such  a  combination  will 
be  easily  understood,  when  it  is  remembered  that  each  of  the 
innumerable  closed  chains  of 

Fig.  79. 

moving  molecules  now  ex- 
tends   through    the    whole 
combination,  and  that  all  its 
parts  move  in  the  same  close 
mutual   dependence   as   be- 
fore.    But  whereas  with  a  single  cell  the  motion  throughout 
any  single  chain  of  molecules  is  sustained   by  the   chemical 
energy  at  only  one  point,  it  is  here  reinforced  at  several  points; 


1  From  the  names  of  Galvani  and  Volta,  two  Italian  physicists,  who  first 
investigated  this  class  of  phenomena. 


166     ELECTEICAL  RELATIONS  OF  THE  ATOMS. 

and  the  polar  energy  at  any  point  of  the  circuit  is  the  effect  of 
the  induction  of  the  acid  molecules  between  each  pair  of  plates 
concurring  with  that  produced  by  the  similar  molecules  between 
every  other  pair.  The  electro-motive  power  is  then  increased 
in  proportion  to  the  number  of  cells;  and  the  effect  on  the  cur- 
rent would  be  increased  in  the  same  proportion,  were  it  not  for 
the  fact  that  the  current  must  keep  in  motion  a  greater  mass  of 
liquid,  and  hence  the  resistance  is  increased  at  the  same  time. 
The  value  of  this  resistance,  however,  is  easily  estimated,  since 
it  is  directly  proportional  to  the  distance  through  which  the  cur- 
rent has  to  flow  in  the  liquid  ;  and  hence,  if  the  liquid  is  the 
same  in  all  the  cells,  and  the  plates  are  at  the  same  distance 
apart  in  each,  the  liquid  resistance  will  be  n  times  as  great  in  a 
combination  of  n  cells  as  it  is  in  one.  Moreover,  since  the  effec- 
tive electro-motive  force  is  n  times  as  great  also,  while  the  ex- 
ternal resistance  remains  unchanged,  the  strength  of  the  current 
from  such  a  combination  will  still  be  expressed  by  formula  [62] 
slightly  modified. 


This  formula  shows  at  once,  that,  when  the  exterior  resist- 
ance is  very  small,  or  nothing,  very  little  or  no  gain  will  result 
from  increasing  the  number  of  cells,  for  the  ratio  of  nE  to  nR 
is  the  same  as  that  of  E  to  R  ;  and,  under  such  conditions,  in 
order  to  increase  the  strength  of  the  current,  we  must  increase 
the  surface  of  the  plates.  If,  on  the  contrary,  the  exterior  re- 
sistance is  very  large,  the  formula  shows  that  great  gain  will 
result  from  increasing  the  number  of  the  cells,  and  that  little 
or  no  advantage  will  accrue  from  enlarging  the  surface  of  the 
plates.  Moreover,  the  formula  enables  us  in  any  case  to  de- 
termine what  proportion  the  number  of  cells  should  bear  to  the  • 
size  of  the  plates  in  order  to  obtain  the  full  effect  of  any  battery 
in  doing  a  given  work;  and  in  the  numerous  applications  of 
electricity  in  the  arts  we  find  abundant  illustrations  of  the 
principles  it  involves.  The  methods  used  in  finding  the  values 
of  the  quantities  represented  in  the  formula  lie  beyond  the 
scope  of  this  work,  and  for  such  information  the  student  is  re- 
ferred to  works  on  Physics. 

90.    Constructions  of  Cells.  —  It  is  found  practically  that  the 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.  167 

simple  combination  of  plates  and  acid  first  described  must  be 
slightly  modified  in  order  to  obtain  the  best  results. 

In  the  first  place,  both  the  zinc  and  sulphuric  acid  of  com- 
merce contain  impurities,  which  give  rise  to  what  is  called 
local  action,  and  cause  the  zinc  to  dissolve  in  the  acid  when 
the  battery  is  not  in  action.  Fortunately,  however,  it  has  been 
found  that  such  local  action  can  be  wholly  prevented  by  care- 
fully amalgamating  the  surface  of  the  zinc  and  filtering  the 
acidulated  water. 

The  mercury  on  the  surface  of  the  zinc  plates  acts  as  a  sol- 
vent, and  gives  a  certain  freedom  of  motion  to  the  particles 
of  the  metal.  These,  by  the  action  of  the  polar  forces,  are 
brought  to  the  surface  of  the  plate,  while  the  impurities  are 
forced  back  towards  the  interior,  so  that  the  plate  constantly 
exposes  a  surface  of  pure  zinc  to  the  action  of  the  acid. 

By  filtering  we  remove  the  particles  of  plumbic  sulphate 
which  remain  floating  in  the  sulphuric  acid  for  a  long  time 
after  it  has  been  diluted  with  water,  and  which,  when  deposited 
on  the  surface  of  the  zinc,  become  points  of  local  action,  even 
when  the  plates  have  been  carefully  amalgamated. 

In  the  second  place,  the  continued  action  of  the  simple  com- 
bination first  described  develops  conditions  which  soon  greatly 
impair,  and  at  last  wholly  destroy,  its  efficiency. 

The  hydrogen  gas,  which  by  the  action  of  the  current  is 
evolved  at  the  platinum  plate,  adheres  strongly  to  its  surface, 
and  with  its  powerful  affinities  draws  back  the  lines  of  atoms 
moving  towards  the  zinc  plate,  and  thus  diminishes  the  effec- 
tive electro-motive  force.  Moreover,  after  the  battery  has  been 
working  for  some  time,  the  water  becomes  charged  with  zincic 
sulphate  ;  and  then  the  zinc,  following  the  course  of  the  hydro- 
gen, is  also  deposited  on  the  surface  of  the  platinum,  which 
after  a  while  becomes,  to  all  intents  and  purposes,  a  second 
zinc  plate,  and  then,  of  course,  the  electric  current  ceases. 

Both  of  these  difficulties,  however,  have  also  been  sur- 
mounted by  a  very  simple  means  discovered  by  Mr.  Grove,  of 
London.  The  Grove  cell,  Fig.  80,  consists  of  a  circular  plate  of 
zinc  well  amalgamated  on  its  surface,  and  immersed  in  a  glass 
jar  containing  dilute  sulphuric  acid.  Within  the  zinc  cylinder  is 
placed' a  cylindrical  vessel  of  much  smaller  diameter,  made  of 
porous  earthenware,  and  filled  with  the  strongest  nitric  acid, 


168 


ELECTRICAL  RELATIONS  OF  THE  ATOMS. 


and  in  this  hangs  the  plate  of  platinum,  Fig.  81.     The  walls  of 


Fig.  81. 


the  porous  cell  allow  both  the  hydrogen  and  the  zinc  atoms  to 
pass  freely  on  their  way  to  the  platinum  plate  ;  but  the  moment 
they  reach  the  nitric  acid  they  are  at  once  oxidized,  and  thus 
the  surface  of  the  platinum  is  kept  clean,  and  the  cell  in  condi- 
tion to  exert  its  maximum  electro-motive  power.  In  this  com- 
bination we  may  substitute  for  the  plate  of  platinum  a  plate 
of  dense  coke,  such  as  forms  in  the  interior  of  the  gas  retorts, 
which  is  very  much  cheaper,  and  enables  us  to  construct  large 
cells  at  a  moderate  cost.  The  use  of  gas  coke  was  first  sug- 
gested by  Professor  Bunsen  of  Heidelberg,  and  the  cell  so 
constructed  generally  bears  his  name.  The  Bunsen  cell,  such 
as  is  represented  in  Fig.  82,  is  exceedingly  well  adapted  for  use 

Fig.  82. 


in  the  laboratory.     These  cells  are  usually  made  of  nearly  a 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.      169 

uniform  size,  the  zinc  cylinders  being  about  8  c.  m.  in  diameter 
by  22  c.  m.  high,  and  they  are  frequently  referred  to  as  a  rough 
standard  of  electrical  power.  They  may  be  united  so  as  to 
produce  effects  either  of  intensity  or  of  quantity.  The  inten- 
sity effects  are  obtained  in  the  manner  already  described  (see 
Fig.  79),  and  the  quantity  effects  are  obtained  with  equal  readi- 
ness ;  since  by  attaching  the  zinc  of  several  cells  to  the  same 
metallic  conductor,  and  the  corresponding  coke  plates  to  a 
similar  conductor,  we  have  the  equivalent  of  one  cell  with  large 
plates.  Many  other  forms  of  battery,  differing  in  more  or  less 
important  details  from  those  here  described,  and  adapted  to 
special  applications  of  electricity,  are  used  in  the  arts,  and  are 
fully  described  in  the  larger  works  on  physics. 

91.  Electrolysis.  —  As  our  theory  indicates,  the  electrical 
current  has  the  remarkable  power  of  imparting  to  the  unlike 
atoms  of  almost  all  compound  bodies  motion  in  opposite  direc- 
tions, like  that  in  the  battery  cell  itself,  and  this,  too,  at  what- 
ever point  in  the  circuit  they  may  be  introduced.  The  galvanic 
battery  thus  becomes  a  most  potent  agent  in  producing  chemi- 
cal decompositions,  and  it  is  in  consequence  of  this  fact  that  the 
theory  of  the  instrument  fills  such  an  important  place  in  the  phi- 
losophy of  chemistry. 

If  we  break  the  metallic  conductor  at  any  point  of  a  closed 
circuit,  the  two  ends,  which  in  chemical  experiments  we  usually 
arm  with  platinum  plates,1  are  called  poles.  The  end  con- 
nected with  the  platinum  or  coke  plate,  from  which  the  positive 
current  is  assumed  to  flow,  is  called  the  positive  pole,  and  the 
end  connected  with  the  zinc  plate,  from  which  the  negative 
current  flows,  is  called  the  negative  pole.  Let  us  assume 
that  Fig.  83  represents  the  two  platinum  poles  dipping  in  a 
solution  of  hydrochloric  acid  in  water,  which 
thus  becomes  a  part  of  the  circuit.  The  Fis-  83< 

moment  the  circuit  is  thus  closed,  the  /Tand 
Cl  atoms  begin  to  travel  in  opposite  direc- 
tions, just  as  in  the  battery  cell  below.  The 
hydrogen  atoms  move  with  the  positive  cur- 
rent towards  the  negative  pole,  and  hydro- 
gen gas  is  disengaged  from  the  surface  of 

1  We  use  platinum  plates  because  this  metal  does  not  readily  enter  into 
combination  with  the  ordinary  chemical  agents. 


170      ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

the  negative  plate,  while  the  chlorine  atoms  move  with  the 
negative  current  towards  the  positive  pole,  and  chlorine  gas 
is  evolved  from  the  surface  of  the  positive  plate.  More- 
over, it  will  be  noticed  that  each  kind  of  atoms  moves  in  the 
same  direction  on  the  closed  circuit,  that  is,  follows  the  course 
of  the  same  current,  both  in  the  battery  cell  below  and  in  the 
decomposing  cell  above ;  and  wherever  we  break  the  circuit, 
and  at  as  many  places  as  we  may  break  it,  the  same  phenomena 
may  be  produced,  provided  only  that  our  battery  has  sufficient 
power  to  overcome  the  resistance  thus  introduced. 

If  next  we  dip  the  poles  in  water,  the  atoms  of  the  water 
will  be  set  moving,  as  shown  in  Fig.  84;  hy- 
c      drogen  gas  escaping  as  before  from  the  neg- 

Iative  pole,  and  oxygen  gas  from  the  positive. 
We  find,  however,  that  pure  water  opposes 
a  very  great  resistance  to  the  motion  of  the 
_  current ;  and,  unless  the  current  has  great 
intensity,  the  effects  obtained  are  inconsider- 
able. But  if  we  mix  with  the  water  a  little  sulphuric  acid,  the 
decomposition  at  once  becomes  very  rapid ;  but  then  it  is  the 
atoms  of  the  sulphuric  acid,  and  not  those  of  the  water,  which 
are  set  in  motion.  The  molecule  H2SO±  divides  into  ff2  and 
SOi ;  the  hydrogen  atoms  moving  in  the  usual  direction,  and 
the  atoms  of  S04  in  the  opposite  direction.  As  soon,  however, 
as  the  last  are  set  free  at  the  positive  pole,  they  come  in 
contact  with  water,  which  they  immediately  decompose, 
1  2ff20+2S04=2ff2S04+  0=0,  and  the  oxygen  gas  thus 
generated  escapes  from  the  face  of  the  platinum  plate.  Thus 
the  result  is  the  same  as  if  water  were  directly  decomposed, 
but  the  actual  process  is  quite  different. 

So  also  in  many  other  cases  of  electrolysis,  —  as  these  decom- 
positions by  the  electrical  current  are  called,  —  the  process  is 
complicated  by  the  reaction  of  the  water,  which  is  the  usual 
medium  employed  in  the  experiments.  Thus,  if  we  interpose 
between  the  poles  a  solution  of  common  salt,  Na  Cl,  the  chlorine 
atoms  move  towards  the  positive  pole,  and  chlorine  gas  is  there 
evolved  as  in  the  first  example.  The  sodium  atoms  move  also, 
but  in  the  opposite  direction.  As  soon,  however,  as  they  are 
set  free  at  the  negative  pole,  they  decompose  the  water  present; 
hydrogen  gas  is  formed,  which  escapes  in  bubbles  from  the 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.      171 

platinum  plate,  while  sodic  hydrate  (caustic  soda)  remains  in 
solution, 

a-0       H-H. 


^ 

| 
c\  so*  B£  8£  s°*      I 


We  add  but  one  other  example,  which  illustrates  a  very 
important  application  of  these  principles  in  the  arts.  We  as- 
sume, in  Fig.  85,  that  the  positive 
pole  is  armed  with  a  plate  of  copper,  ^  Flgl 

and  that  to  the  negative  pole  has  been 

fastened  a  mould  of  some  medallion  c\  so*  B£  8£  s°*  I  \ 
we  wish  to  copy,  the  surface  of  which, 
at  least,  is  a  good  conductor.  We 
assume  further  that  both  copper  plate  and  mould  are  sus- 
pended in  a  solution  of  sulphate  of  copper,  Gu=S04.  In  this 
case  the  atoms  of  the  compound  are  set  in  motion  as  before. 
Those  of  copper  accumulate  on  the  surface  of  the  mould  ;  and 
at  last  the  coating  will  attain  such  thickness  that  it  can  be  re- 
moved, furnishing  an  exact  copy  of  the  original  medallion. 
Meanwhile  the  atoms  of  S0±  have  found  at  the  positive 
pole  a  mass  of  copper,  with  whose  atoms  they  have  combined  ; 
and  thus  fresh  sulphate  of  copper  has  been  formed,  and  the 
solution  replenished.  The  process  has  in  effect  consisted  in 
a  transfer  of  metal  from  the  copper  plate  to  the  medallion  ; 
and,  by  using  appropriate  solvents,  silver  and  gold  can  be 
transferred  and  deposited  in  the  same  way. 

In  all  these  processes  of  electrolysis,  one  remarkable  fact  has 
been  observed,  which  has  a  very  important  bearing  on  the 
theory  of  the  battery.  If  in  any  given  circuit  we  introduce  a 
number  of  decomposing  cells,  containing  acidulated  water,  we 
find  that  in  a  given  time  exactly  the  same  amount  of  gas  is 
evolved  in  each  ;  thus  proving,  what  we  have  thus  far  assumed, 
that  the  moving  power  is  absolutely  the  same  at  all  points  on 
the  circuit.  Moreover,  the  amount  of  gas  which  is  evolved 
from  such  a  decomposing  cell  in  the  unit  of  time  is  an  ac- 
curate measure  of  the  strength  of  the  current  actually  flowing 
in  any  circuit,  and  this  mode  of  measuring  the  quantity  of  an 
electrical  current  is  constantly  used. 

We  should  infer  from  the  facts  already  stated,  and  the  prin- 
ciple has  been  confirmed  by  the  most  careful  experiments,  that 
the  chemical  changes  which  may  take  place  at  different  points 


172      ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

of  the  same  closed  circuit  are  always  the  exact  equivalents  of 
each  other.  If,  for  example,  we  have  a  series  of  Grove's  cells, 
arranged  as  in  Fig.  79,  and  interpose  in  the  external  circuit 
two  decomposing  cells,  as  in  Figs.  84  and  85,  we  shall  find 
(provided  there  is  no  local  action)  that  the  weight  of  zinc  dis- 
solved in  each  of  the  five  Grove's  cells  is  the  exact  chemical 
equivalent,  (26)  not  only  of  the  weight  of  hydrogen  gas  evolved 
from  the  first  decomposing  cell,  but  also  of  the  weight  of  me- 
tallic copper  deposited  on  the  mould  in  the  second.  For  every 
63.4  grammes  of  copper  deposited,  2  grammes  of  hydrogen  are 
evolved,  and  65.2  grammes  of  zinc  are  dissolved  in  each  cell 
of  the  battery.  If  there  is  also  local  action  in  the  cells,  the 
chemical  change  thus  induced  is  added  to  the  normal  effect  of 
the  battery-current. 

This  important  principle  (discovered  by  Faraday)  is  in  entire 
harmony  with  the  theory  of  electricity  developed  in  this  chap- 
ter. In  the  single  Voltaic  cell,  Fig.  77,  there  is  but  one  source 
of  free  electricity,  which  all  flows  through  the  same  conductor, 
In  a  Voltaic  battery,  Fig.  79,  there  are  as  many  sources  of  free 
electricity  as  there  are  separate  cells ;  but  only  the  free  elec- 
tricity received  on  the  end  plates  flows  through  the  longer  con- 
ductor,1 for  that  received  on  the  intermediate  plates  becomes 
neutralized  in  the  shorter  conductors1  uniting  the  cells.  In 
either  case,  if  a  liquid  forms  a  part  of  the  principal  conductor, 
as  in  Fig.  83,  then  the  molecules  of  the  liquid  decomposed  by 
the  current  become  an  additional  source  of  electricity,  and  the 
currents  flowing  from  the  two  ends  of  the  battery  are  neutral- 
ized by  the  charges  of  electricity,  which  the  atoms  liberated  from 
the  electrolyte  2  bring  with  them  to  either  electrode.2  Thus,  in 
Fig.  83,  the  positive  electricity  flowing  from  the  inactive  plate 
of  the  battery  is  neutralized  by  the  negative  electricity,  which 
the  chlorine  atoms  yield,  and  the  negative  electricity  from  the 
active  plate  of  the  battery  by  the  positive  electricity,  which  the 
hydrogen  atoms  yield.  Now,  since,  according  to  our  theory,  the 
strength  of  a  current  is  necessarily  the  same  at  all  points  of  a 

1  It  will  be  noticed  that  each  of  the  five  conductors  in  Fig.  79  sustains  the 
same  relations  to  the  battery  as  a  whole. 

2  The  liquid  submitted  to  electrolysis  is  frequently  called  an  electrolyte^  and 
the  inactive  poles  dipping  into  the  liquid  are  also  called  electrode*. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.      173 

continuous  circuit,  however  extended,  and  since  the  amount  of 
electricity  set  free  in  the  decomposing  cell,  as  in  the  battery 
cells,  must  be  proportional  to  the  number  of  atomic  bonds 
broken  (86),  it  is  evident  that  it  would  require,  for  example, 
twice  as  many  hydrogen  as  copper  atoms,  liberated  on  the  face 
of  an  electrode  in  a  given  time,  to  supply  the  same  current,  and 
this  is  equivalent  to  the  principle  stated  above. 

The  examples  which  have  been  given  are  sufficient  to  illus- 
trate the  remarkable  power  which  the  electric  current  possesses 
of  setting  in  motion  the  atoms  of  compound  bodies.  Innumer- 
able experiments  have  shown  that,  in  reference  to  their  rela- 
tions to  the  current,  the  atoms,  both  simple  and  compound,  may 
be  divided  into  two  great  classes :  first,  those  whicn  travel  on 
the  line  of  the  circuit  in  the  direction  of  the  positive  current 
and  follow  hi  the  lead  of  the  hydrogen  atoms  ;  and,  secondly, 
those  which  follow  the  lead  of  the  chlorine  atoms,  and  move  in 
the  opposite  direction  with  the  negative  current.  The  first 
class  of  atoms,  or  radicals,  we  call  positive  ;  and  the  second  class, 
negative. 

The  opposition  in  qualities  of  the  chemical  atoms,  which  the 
study  of  these  electrical  phenomena  has  revealed,  is,  in  many 
cases  at  least,  relative,  and  not  absolute.  For,  while  there  are 
some  atoms  which  always  manifest  the  same  character,  there 
are  others  which  appear  in  some  associations  positive,  and  in 
other  associations  negative.  To  such  an  extent  is  this  true, 
that  the  electrical  relations  of  the  atoms  are  best  shown  by 
grouping  the  elements  in  series,  which  may  be  so  arranged  that 
each  member  of  the  series  shall  be  electro-positive  when  in 
combination  with  those  elements  which  follow  it,  and  electro- 
negative when  combined  with  those  which  precede  it. 

NOTE.  —  Questions  and  problems  bearing  on  this  chapter  will 
be  found  in  the  Appendix,  page  567. 


CHAPTEE    XVI. 

RELATIONS    OF   THE   ATOMS    TO   LIGHT. 

92.  Light  a  Mode  of  Atomic  Motion.  —  It  has  already  been 
intimated  (§  61,  note),  that  the  phenomena  of  vision  are  the 
effects  of  an  atomic  motion  transmitted  from  some  luminous 
body  to  the  eye  through  continuous  lines  of  material  particles, 
and  such  lines  we  call  rays  of  light.  This  motion  may  origi- 
nate with  the  atoms  of  various  substances  ;  but  in  order  to 
explain  its  transmission,  we  are  obliged  to  assume  the  existence 
of  a  medium  filling  all  space,  of  extreme  tenuity,  and  yet 
having  an  elasticity  sufficiently  great  to  transmit  the  luminous 
pulsations  with  the  incredible  velocity  of  186,000  miles  in  a 
second  of  time.  This  medium  we  call  the  ether,  but  of  its 
existence  we  have  no  definite  knowledge  except  that  obtained 
through  the  phenomena  of  light  themselves,  and  these  require 
assumptions  in  regard  to  the  constitution  of  the  ethereal  medium 
which  are  not  realized  even  approximately  in  the  ordinary 
forms  of  matter ;  for  while  the  assumed  medium  must  be 
vastly  less  dense  than  hydrogen,  its  elasticity  must  surpass  that 
of  steel. 

According  to  the  undulatory  theory,  motion  is  transmitted 
from  particle  to  particle  along  the  line  of  each  luminous  wave 
very  much  in  the  same  way  that  it  passes  along  the  line  of 
ivory  balls  in  the  well-known  experiment  of  mechanics.  The 
ethereal  atoms  are  thus  thrown  into  waves,  and  the  order  of 
the  phenomena  is  similar  to  that  with  which  all  are  familiar 
in  the  grosser  forms  of  wave  motion.  But  in  this  connection 
we  have  no  occasion  to  dwell  on  the  mechanical  conditions 
attending  the  transmission  of  the  motion.  The  motion  itself 
may  be  best  conceived  as  an  oscillation  of  each  ether  particle 
in  a  plane  perpendicular  to  the  direction  of  the  ray,  not 


RELATIONS   OF   THE  ATOMS   TO  LIGHT.  175 

necessarily,  however,  in  a  straight  line  ;  for  the  orbit  of  the 
oscillating  molecule  may  be  either  a  straight  line,  an  ellipse,  or  a 
circle,  as  the  case  may  be.  Such  oscillations  may  evidently 
differ  both  as  regards  their  amplitude  and  their  duration,  and 
on  these  fundamental  elements  depend  two  important  differences 
in  the  effect  of  the  motion  on  the  organs  of  vision,  viz.  intensity 
and  quality,  or  brilliancy  and  color. 

If  our  theory  is  correct,  it  is  obvious  that  the  intensity  of 
the  luminous  impression  must  depend  upon  the  force  of  the 
atomic  blows  which  are  transmitted  to  the  optic  nerves,  and  it 
is  also  evident  that  this  force  must  be  proportional  to  the 
square  of  the  velocity  of  the  oscillating  atoms,  or  what  amounts 
to  the  same  thing,  to  the  square  of  the  amplitude  of  the 
oscillation ;  assuming,  of  course,  that  the  oscillations  are 
isochronous. 

The  connection  of  color  with  the  time  of  oscillation  is  not  so 
obvious,  and  why  it  is  that  the  waves  of  ether  beating  with 
greater  or  less  rapidity  on  the  retina  should  produce  such 
sensations  as  those  of  violet,  blue,  yellow,  or  red,  the  physiologist 
is  wholly  unable  to  explain.  We  have,  however,  an  analogous 
phenomenon  in  sound,  for  musical  notes  are  simply  the  effects  of 
waves  of  air  beating  in  a  similar  way  on  the  auditory  nerves ; 
and,  as  is  well  known,  the  greater  the  frequency  of  the  beats, 
or,  in  other  words,  the  more  rapid  the  oscillations  of  the 
aerial  molecules,  the  higher  is  the  pitch  of  the  note.  Red 
color  corresponds  to  low,  and  violet  to  high  notes  of  music, 
and,  the  gradations  of  color  between  these  extremes,  passing 
through  various  shades  of  orange,  yellow,  green,  blue,  and 
indigo,  correspond  to  the  well-known  gradations  of  musical 
pitch. 

From  well-established  data  -we  are  able  to  calculate  the 
rapidity  of  the  oscillations  which  produce  the  different  sensa- 
tions of  color,  and  also  to  estimate  the  corresponding  lengths 
of  the  ether  waves,  and  the  following  table  contains  the 
results.  It  must  be  understood,  however,  that  these  numbers 
merely  correspond  to  a  few  shades  of  color  definitely  marked 
on  the  solar  spectrum  by  certain  dark  lines  hereafter  to  be  men- 
tioned ;  and  that  equally  definite  values  may  be  assigned  to 
the  infinite  number  of  intermediate  shades  which  intervene 
between  these  arbitrary  subdivisions  of  the  chromatic  scale. 


176  RELATIONS   OF   THE  ATOMS  TO  LIGHT. 

Number  of  waves  or  oscilla-          Length  of  waves  in  frac- 
Color.  tions  in  one  second.  tions  of  a  millimetre. 

Red  477  million  million.  650  millionths. 

Orange  506  "  «  609  « 

Yellow  535  "  "  576  " 

Green  577  "  "  536  " 

Blue  622  «  "  498  " 

Indigo  658  "  u  470  " 

Violet  699  "  "  442  " 

93.  Natural  Colors.  —  It  follows,  as  a  necessary  consequence 
of  the  fundamental  laws  of  mechanics,  that  an  oscillating  mole- 
cule can  only  transmit  to  its  neighbor  motion  which  is  isochronous 
with  its  own.  Hence  a  single  ray  of  light  can  only  produce  a  def- 
inite effect  of  color,  and  this  quality  of  the  ray  will  be  preserved 
however  far  the  motion  may  travel.   A  beam  of  light  is  simply 
a  bundle  of  rays,  and  if  the  motion  is  isochronous  in  all  its 
parts,  that  is,  if  the  beam  consists  only  of  rays  of  .one  shade  of 
color,  such  a  beam  will  produce  the  simplest  chromatic  sensa- 
tion possible,  —  that  of  a  pure  color.     If,  however,  the  beam 
contains  rays  of  different  colors,  we  shall  have  a  more  complex 
effect,  and  the  infinite  variety  of  natural  tints  are  thus  produced. 
When,  lastly,  the  beam  contains  rays  of  all  the  colors  mingled 
in  due  proportion,  we  receive  an  impression  in  which  no  single 
color  predominates,  and  this  we  call  white  light. 

The  colors  of  natural  objects,  whether  inherent  or  imparted 
by  various  dyes,  are  simply  effects  upon  the  retina  produced  by 
the  beam  after  it  has  been  reflected  from  the  surface  or  trans- 
mitted through  the  mass  of  the  body,  and  the  peculiar  chromatic 
effects  are  due  to  the  unequal  proportions  in  which  the  dif- 
ferent colored  rays  are  thus  absorbed.  The  color  reflected,  and 
that  absorbed  or  transmitted,  are  always  complementary  to 
each  other,  and  if  mingled  they  would  reproduce  white.  It  is 
obvious,  moreover,  that  no  beam  of  light,  however  modified  by 
reflection  or  transmission,  could  produce  the  sensation  of  a 
given  color,  if  it  did  not  contain  from  the  first  the  correspond- 
ing colored  rays.  Hence  it  is  that  the  colors  of  objects  only 
appear  naturally  by  daylight,  and  when  illuminated  by  a 
monochromatic  light,  all  colors  blend  in  that  of  this  one  pure 
tint. 

94.  Chromatic  Spectra  and  Spectroscopes.  —  When  a  beam 
of  light  is  passed  through  a  glass  prism  placed  as  shown  in  Fig. 


RELATIONS  OF  THE  ATOMS  TO  LIGHT. 


177 


Fig.  86. 


86,  it  is  not  only  refracted,iha,t  is,  bent  from  its  original  rectilinear 
course,  but  the  colored  rays  of  which  the  beam  consists,  being 
bent  unequally,  are  separated  to  a  greater  or  less  extent,  and  fall- 
ing on  a  screen  produce  an  elongated  image  colored  with  a  suc- 
cession of  blending  tints,  which  we  call  the  spectrum.  The  red 
rays,  which  are  bent  the  least,  are  said  to  be  the  least  refran- 
gible, while  the  violet  rays  are  the  most  refrangible,  and  inter- 
mediate between  these  we  have,  in  the  order  of  refrangibility, 
the  various  tints  of  orange,  yellow,  green,  blue,  and  indigo. 
Thus  a  prism  gives  an  easy  means  of  analyzing  a  beam  of 
light,  and  of  discovering  the  character  of  the  rays  by  which  a 
given  chromatic  effect  is  produced.  Such  observations  are 
very  greatly  facilitated  by  a  class  of  instruments  called  spectro- 
scopes, and  Figs.  87  and  90  will  illustrate  the  principles  of 
their  construction. 

In  the  very  powerful  instrument  first  represented,  the  beam 
of  light  is  passed  in  succession  through  nine  prisms  (each 
having  an  angle  of  45°),  and  the  extreme  rays  are  thus  widely 
separated,  while  the  beam  itself  is  bent  around  nearly  a  whole 
circumference.  The  only  other  essential  parts  of  the  instru- 
ment are  the  collimator  A  and  the  telescope  B.  The  light  first 
enters  the  collimator  through  a  narrow  slit,  and  having  passed 
through  the  prisms  is  received  by  the  telescope.  The  tele- 
scope is  adjusted  as  it  would  be  for  viewing  distant  objects, 


178 


RELATIONS  OF  THE  ATOMS  TO  LIGHT. 


and  a  lens  at  the  end  of  the  collimator  serves  to  render  the 
rays  diverging  from  the  slit  parallel,  so  that  when  the  two 

Fig.  87. 


tubes   are  in   line,   one   sees   through   the  telescope  a  mag- 
nified image  of  the  slit,  just  as  if  the  slit  were  at  a  great 


Fig.  88. 


distance.     In  like  manner  when  the  telescopes  are  placed  as 
in  Fig.  88,  and  when  the  light  before  reaching  the  telescope 


RELATIONS   OF   THE   ATOMS   TO  LIGHT.  179 


HH 


••mi'   '  •••m 


|Ora-|Yel-|      Green.      i  Blue.  I 

Inge.  I  low.  I  I  I 

passes  through  the  whole  series  of  prisms,  we  still  see  a  single 
definite  image  whenever  the  slit  is  illuminated  by  a  pure 
monochromatic  light.  Moreover,  this  image  has  a  definite 
position  in  the  field  of  view,  which,  when  the  instrument  is 
similarly  adjusted,  depends  solely  on  the  refrangibility  of  the 
light. 

Thus,  if  we  place  in  front  of  the  slit  a  sodium  flame,  which 
emits  a  pure  yellow  light,  we  see  a  single  yellow  image  of  this 
longitudinal  opening,  as  in  Fig.  89,  Na.  If  we  use  a  lithium 
flame,  we  see  a  similar  image,1  but  colored  red,  and  at  some 
distance  from  the  first,  to  the  left,  if  the  parts  of  our  in- 
strument are  disposed  as  in  Fig.  88.  If  we  use  a  thalium 
flame,  we  in  like  manner  see  a  single  image,  but  colored 
green,  and  falling  considerably  to  the  right  of  both  of  the 
other  two.  If  now  we  illuminate  the  slit  by  the  three 
flames  simultaneously,  we  see  all  three  images  at  once  in  the 
same  relative  position  as  before.  So  also  if  we  examine  the 
i  The  second  image  shown  in  Fig.  89,  Li  ia  not  ordinarily  seen. 


180  RELATIONS   OF   THE  ATOMS   TO   LIGHT. 

flame  of  a  metal,  which  emits  rays  of  several  definite  degrees 
of  refrangibility,  we  see  an  equal  number  of  definite  images 
of  the  slit.  If,  next,  we  illuminate  the  slit  with  sunlight, 
which  contains  rays  of  all  degrees  of  refrangibility,  we  see  an 
infinite  number  of  images  of  the  slit  spread  out  along  the  field 
of  view,  and  these,  overlapping  each  other,  form  that  continuous 
band  of  blending  colors  which  we  call  the  solar  spectrum.  If, 
lastly,  we  examine  with  our  instrument  the  light  reflected  from 
a  colored  surface,  or  transmitted  through  a  colored  medium, 
we  also  see  a  band  of  blending  colors,  but  at  the  same  time  we 
observe  that  certain  portions  of  the  normal  solar  spectrum  are 
either  wholly  wanting  or  greatly  obscured. 

With  a  spectroscope  of  many  prisms  like  the  one  represented 
by  Fig.  87,  we  can  only  see  a  small  portion  of  the  spectrum  at 
once.  By  moving  the  telescope,  which,  fastened  to  a  metallic 
arm,  revolves  around  the  axis  of  the  instrument,  different 
portions  of  the  spectrum  may  be  brought  into  the  field  of  view  ; 
while  a  vernier,  attached  to  the  same  arm  and  moving  over  a 
graduated  arc,  enables  us  to  fix  the  position  of  the  spectrum 
lines,  as  the  images  of  the  slit  are  usually  called.  The  other 
mechanical  details  shown  in  the  figure  are  required  in  order 
to  adjus)  the  various  parts  of  the  instrument,  and  especially  in 
order  to  bring  the  prisms  to  what  is  termed  the  angle  of 
minimum  deviation.  But  an  instrument  of  this  magnitude  and 
power  is  not  required  for  the  ordinary  applications  of  the 
spectroscope  in  chemistry.  For  this  purpose  a  small  instru- 
ment consisting  of  a  collimator,  a  single  prism,  and  a  telescope, 
all  in  a  fixed  position,  are  amply  sufficient.  In  the  field  of  such 
a  spectroscope  the  whole  spectrum  may  be  seen  at  once  ;  and 
the  position  of  the  spectrum  lines  is  very  easily  determined  by 
means  of  a  photographic  scale  placed  at  one  side,  and  seen  by 
light  reflected  into  the  telescope  from  the  face  of  the  prism. 

The  various  parts  of  the  instrument,  as  arranged  for  ob- 
servation, are  shown  in  Fig.  90.  A  is  the  collimator,  P  the 
prism,  and  B  the  telescope.  The  tube  C  carries  the  photo- 
graphic scale,  and  has  at  the  end  nearest  to  the  prism  a 
lens  of  such  focal  length  that  the  image  both  of  the  slit  and 
the  scale  may  be  seen  through  the  telescope  at  the  same  time, 
the  one  appearing  projected  upon  the  other.  The  screw  e 
serves  to  adjust  the  width  of  the  slit.  Moreover,  one  half  of  the 


RELATIONS  OF  THE  ATOMS  TO  LIGHT.  181 

Tig.  90. 


length  of  the  slit  is  covered  by  a  small  glass  prism  so  arranged 
that  it  reflects  into  the  collimator  tube  the  rays  from  a  lamp 
placed  on  one  side.  Thus  the  two  halves  of  the  slit  may  be 
illuminated  independently  by  light  from  different  sources,  and 
the  two  spectra,  which  are  then  seen  superimposed  upon  each 
other  (see  Fig.  91),  exactly  compared.  The  various  screws, 
which  appear  in  Fig.  90,  are  used  for  adjusting  the  different 
parts  of  the  instrument. 

95.  Spectrum  Analysis.  —  The  atoms  of  the  different  chem- 
ical elements,  when  rendered  luminous  under  certain  definite 
conditions,  always  *  emit  light  whose  color  is  more  or  less 
characteristic,  and  which,  when  analyzed  with  the  spectroscope, 
exhibit  spectra  similar  to  those  which  are  represented  in  Fig. 
89,  so  far  as  is  possible  without  the  aid  of  color.  Sometimes 
we  see  only  a  single  line  in  a  definite  position,  as  in  the  case 
of  Na,  Li,  and  Th,  already  referred  to.  At  other  times 
there  are  several  such  lines  ;  and,  still  more  frequently,  to 
these  lines  (or  definite  images  of  the  slit)  there  are  super- 
added  more  or  less  extended  portions  of  a  continuous  spectrum. 
Moreover,  not  only  is  the  general  aspect  of  each  spectrum 
exceedingly  characteristic,  but  also  the  occurrence  of  its 
peculiar  lines  is,  so  far  as  we  know,  an  absolute  proof  of  the 


182  RELATIONS  OF  THE  ATOMS  TO  LIGHT. 

presence  of  a  given  element,  and  these  lines  may  be  readily 
recognized  by  their  position,  even  when  the  character  of  the 
spectrum  is  otherwise  obscure.  It  is  evident  then  that  we 
have  here  a  principle  which  admits  of  most  important  ap- 
plications in  chemical  analysis,  and  it  only  remains  to  con- 
sider under  what  conditions  the  elementary  atoms  emit  their 
characteristic  light. 

First.  All  bodies  when  intensely  heated  are  rendered  lumi- 
nous, and,  other  things  being  equal,  the  higher  the  temperature 
the  more  intense  is  the  light.  The  brilliancy  of  the  light 
emitted  at  the  same  temperature  by  different  bodies  varies 
very  greatly,  the  densest  bodies  being,  as  a  general  rule,  the 
most  intensely  luminous. 

Secondly.  —  Solid  and  liquid  bodies,  if  opaque,  emit  when 
ignited  white  light,  or  at  least  light  which  shows  with  the  spec- 
troscope a  continuous  spectrum  more  or  less  extended.  At  a 
red  heat  the  light  from  such  bodies  consists  chiefly  of  red  rays, 
but  as  the  temperature  rises  first  to  a  white  and  then  to  a  blue 
heat,  the  more  refrangible  rays  become  more  abundant  and 
finally  predominate. 

Thirdly.  —  The  elementary  substances  give  out  their  pecu- 
liar and  characteristic  light  only  in  the  state  of  gas  or  vapor. 
Hence,  when  we  examine  with  a  spectroscope  a  source  of  light, 
we  may  infer  that  a  continuous  spectrum  indicates  the  presence 
of  solid  or  liquid  bodies,  while  a  discontinuous  spectrum,  with 
definite  lines  or  images  of  the  slit,  indicates  the  presence  of 
gases  and  vapors ;  and  in  the  last  case  we  can,  as  has  been  seen, 
infer  from  the  position  of  the  lines  the  nature  of  the  luminous 
atoms.  It  would  seem,  however,  from  recent  investigations, 
that  under  certain  conditions  even  a  gas  may  show  a  continu- 
ous spectrum,  and  there  are  other  seeming  exceptions  which 
admonish  us  that  the  general  principles  just  stated  should  be 
applied  with  caution. 

Fourthly.  —  At  the  very  high  temperatures  at  which  alone 
gases  or  vapors  become  luminous,  compound  bodies,  as  a  rule, 
appear  to  be  decomposed,  and  the  elementary  atoms  disasso- 
ciated. Hence  the  observations  with  the  spectroscope  have 
been  almost  entirely  confined  to  the  spectra  of  the  elementary 
substances,  and  our  knowledge  of  the  spectra  of  compound  sub- 
stances is  exceedingly  limited.  In  some  few  cases  where  the 


RELATIONS  OF  THE  ATOMS  TO  LIGHT.  183 

spectrum  of  a  compound  has  been  obtained,  it  has  been  noticed 
that,  as  the  temperature  rises,  this  spectrum  is  suddenly  re- 
solved into  the  separate  spectra  of  the  elements  of  which  the 
compound  consists. 

Fifthly.  —  At  a  high  temperature  the  metallic  atoms  of  a 
compound  body  are  far  more  luminous  than  those  of  the  other 
elementary  atoms  with  which  they  are  associated.  Hence, 
when  the  vapor  of  a  metallic  compound  is  rendered  luminous, 
the  light  emitted  is  so  exclusively  that  of  the  metallic  atoms, 
disassociated  by  the  heat,  that  when  examined  with  the  spec- 
troscope the  spectrum  of  the  metal  is  alone  seen ;  and  this  is 
the  probable  explanation  of  the  fact  that  the  sa)ts  of  the  same 
metal,  when  treated  as  will  be  described  in  the  next  para- 
graph, all  show,  as  a  general  rule,  the  same  spectrum  as  the 
metal  itself. 

Lastly.  —  The  substance,  on  which  we  wish  to  experiment, 
may  be  rendered  luminous  in  several  ways.  If  the  substance 
is  a  volatile  metallic  salt,  the  simplest  method  is  to  expose  a 
bead  of  the  substance  (supported  on  a  loop  of  platinum  wire) 
to  the  flame  of  a  Bunsen's  burner  (Fig.  90),  which  by  itself 
burns  with  a  nearly  non-luminous  flame.  The  flame  soon  be- 
comes filled  with  the  disassociated  atoms  of  the  metal  and 
shines  with  their  peculiar  light. 

In  order  to  study  the  spectra  of  the  less  volatile  metals  like 
aluminum,  iron,  or  nickel,  we  use  two  needles  of  the  metal,  and 
pass  between  the  points,  when  about  one  fourth  of  an  inch 
apart,  the  electric  discharges  of  a  powerful  Ruhmkorff  coil, 
condensed  by  a  large  Leyden  jar.  The  metal  is  volatilized 
by  the  heat  of  the  electric  current,  and  the  space  between  the 
points  becomes  filled  with  the  intensely  ignited  vapor,  which 
then  shines  with  its  characteristic  light."1 

In  a  similar  way  we  can  experiment  on  the  permanent  gases 
and  lighter  vapors,  enclosing  them  in  a  glass  tube  with  plati- 
num electrodes,  and  before  sealing  the  tube  reducing  the  ten- 
sion with  an  air  pump,  when  the  discharge  will  pass  through 
a  length  of  several  inches  of  the  attenuated  gas.  The  light 
then  emitted  comes  from  the  atoms  or  molecules  of  the  gas,  and 
where  the  electric  current  is  condensed  as  in  the  capillary  por- 

1  An  electric  spark  is  in  every  case  merely  a  line  of  material  particles  ren- 
dered luminous  by  the  current. 


184  RELATIONS  OF  THE  ATOMS  TO  LIGHT. 

tion  of  the  tubes  constructed  for  this  purpose,  the  light  is  suf- 
ficiently intense  to  be  analyzed  with  the  spectroscope. 

The  three  different  modes  of  experimenting  just  described  do 
not  by  any  means  always  give  the  same  spectrum  when  ap- 
plied to  the  same  chemical  element.  It  constantly  happens 
that  as  the  temperature  rises  new  lines  appear,  which  are  usu- 
ally those  corresponding  to  the  more  refrangible  rays,  and  at 
the  very  high  temperatures  generated  by  the  electric  discharge 
many  of  the  spectra  change  their  whole  aspect.  The  ill-defined 
broad  bands  or  luminous  spaces  which  are  so  conspicuous  at  a 
low  temperature  (see  Fig.  89),  disappear,  and  are  replaced  by 
a  greater  or  less  number  of  definite  spectrum  lines.  Gen- 
erally, however,  the  characteristic  lines  which  mark  the  ele- 
ment at  the  lower  temperature  are  seen  also  at  the  higher ;  but 
sometimes  there  is  a  sudden  and  complete  change  of  the  whole 
spectrum.  The  cause  of  these  differences  is  not  understood, 
but  it  has  been  thought  by  some  investigators  that  the  normal 
spectra  of  the  elementary  atoms  consist  of  bright  bands  alone, 
and  that  the  more  or  less  continuous  spectra,  which  are  also 
seen  at  the  lower  temperatures,  are  to  be  referred  to  the  im- 
perfect disassociation  of  the  atoms,  whose  mutual  attractions 
or  partial  combinations  produce  a  state  of  aggregation  ap- 
proaching the  condition  which  determines  the  continuous  spec- 
tra of  liquid  or  solid  bodies. 

96.  Delicacy   of  the  Method.  —  Having    now  stated    the 
general  principles    of   spectrum   analysis,  and  the  conditions 
under  which  these  principles  may  be  applied,  it  need  only  be 
added  that  the  method  is  one  of  extreme  delicacy.      It  enables 
us  to  detect  wonderfully  minute   quantities   of   many  of   the 
metallic  elements,  and  has  already  led  to  the  discovery  of  four 
elements  of  this  class  which  had  eluded  all  methods  of  investi- 
gation previously  employed.     The  names   of  these   elements, 
Rubidium,  Caesium,   Thallium   and  Indium,  all  refer  to   the 
color  of  their  most  characteristic  spectrum  bands.1 

97.  Solar  and  Stellar  Chemistry.  —  When  a  beam  of  sun- 
light  is    examined   with  a  powerful    spectroscope,  the  solar 
spectrum  is  seen  to  be  crossed  by  an  almost  countless  number 
of  dark  lines  distributed  with  no  apparent  regularity,  and  dif- 

1  The  different  bands  of  the  same  element'  are  usually  distinguished  by 
Greek  letters,  following  the  order  of  relative  brilliancy. 


RELATIONS  OF  THE  ATOMS  TO  LIGHT. 


185 


fering  very  greatly  in  relative  strength  or  intensity.  These 
lines  were  first  accurately  described  by  the  German  optician 
Fraunhofer,  and  have  since  been  known  as  the  Fraunhofer 
lines.  A  few  of  the  most  prominent  of  these  lines  are  shown 
in  Fig.  89,  with  the  letters  of  the  alphabet  by  which  they  are 
designated.  These  lines,  like  the  bright  lines  of  the  elements, 
correspond  in  every  case  to  a  definite  degree  of  refrangibility, 
and  therefore  have  a  fixed  position  on  the  scale  of  the  spectro- 
scope. Moreover,  what  is  very  remarkable,  the  bright  and 
the  dark  lines  have  in  several  cases  absolutely  the  same 
position. 

It  is  easy  to  construct  the  spectroscope  so  that  the  two  halves 
of  the  slit  may  be  illuminated  from  different  sources.  If  then 
we  admit  a  beam  of  sunlight  through  one  half,  and  the  light 
of  a  sodium  flame  through  the  other  half,  we  shall  have  the 
two  spectra  super-imposed  in  the  same  field,  as  in  Fig.  91, 

Fig.  91. 


and  it  will  be  seen  that  the  two  parts  of  the  sodium  band, 
which  appears  as  a  double  line  under  a  high  power,  coincide 
absolutely  in  position  with  the  double  dark  line  D  in  the 
solar  spectrum.  But  a  still  more  striking  coincidence  has 
been  observed  in  the  case  of  iron,  for  the  eighty  well-marked 
bright  lines  in  the  spectrum  of  this  metal  correspond  absolutely 
both  in  position  and  in  strength  with  eighty  of  the  dark  lines 
of  the  solar  spectrum.  Now,  the  chances  that  such  coinci- 
dences are  the  result  of  accident,  are  not  one  in  one  billion 
billion ;  and  we  are  therefore  compelled  to  believe  that  the 
two  phenomena  must  be  connected.  A  simple  experiment 
shows  what  the  relation  probably  is. 

If  we  place  before  the  spectroscope  a  sodium  flame,  we  see, 
of  course,  the  familiar  double  line.     If  now  we  place  behind 


186  RELATIONS  OF  THE  ATOMS  TO  LIGHT. 

the  sodium  flame  a  candle  flame,  so  that  the  candle  also  shines 
into  the  slit,  but  only  through  the  sodium  flame,  we  shall  see 
the  same  bright  lines  projected  upon  the  continuous  spectrum 
of  the  candle.  If,  however,  we  put  in  place  of  the  candle  an 
electric  light,  we  shall  find  that  while  the  continuous  spectrum 
is  now  far  more  brilliant  than  before,  the  sodium  lines  appear 
black.  The  explanation  of  this  singular  phenomenon  is  to  be 
found  in  a  principle,  now  well  established  both  theoretically 
and  experimentally,  that  a  mass  of  luminous  vapor,  while  other- 
wise transparent,  powerfully  absorbs  rays  of  the  same  refrangi- 
bility  which  it  emits  itself.  Hence,  in  our  experiment,  the 
very  small  portion  of  the  spectrum  covered  by  the  sodium  line 
is  illuminated  by  the  sodium  flame  alone,  while  all  the  rest  of 
the  spectrum  is  illuminated  from  the  source  behind,  and  the 
effect  is  merely  one  of  contrast,  the  sodium  lines  appearing 
light  or  dark  according  as  they  are  brighter  or  darker  than  the 
contiguous  portions  of  the  spectrum. 

In  a  similar  way  the  bright  lines  of  a  few  other  elements 
have  been  inverted,  and  these  experiments  would  lead  us  to 
infer  that  the  Fraunhofer  lines  themselves  are  formed  by  a 
brilliant  photosphere  shining  through  a  mass  of  less  luminous 
gas.  In  other  words,  it  would  appear  that  the  sun's  luminous 
orb  is  surrounded  by  an  immense  atmosphere  which  intercepts 
a  portion  of  his  rays,  and  that  we  see  as  dark  lines  what  would 
probably  appear  as  bright  bands,  could  we  examine  the  light 
from  the  atmosphere  alone. 

If  then  our  generalization  is  safe,  the  dark  and  the  bright 
lines  are  the  same  phenomena  seen  under  a  different  aspect, 
and  the  one  as  well  as  the  other  may  be  used  to  identify  the 
different  chemical  elements.  Hence,  then,  there  must  be  both 
iron  and  sodium  in  the  sun's  atmosphere,  and  for  the  same 
reason  we  conclude  that  our  luminary  must  contain  Hydrogen, 
Calcium,  Magnesium,  Nickel,  Chromium,  Barium,  Copper,  and 
Zinc,  while  there  is  equally  good  evidence  that  Gold,  Silver,  Mer- 
cury, Cadmium,  Tin,  Lead,  Antimony,  Arsenic,  Strontium,  and 
Lithium  are  not  present,  at  least  in  large  quantities.  It  is, 
moreover,  worthy  of  notice  that  the  lines  neither  of  oxygen, 
nitrogen,  nor  indeed  of  any  of  that  class  of  bodies  formerly 
called  metalloids,  have  been  recognized  in  the  solar  spectrum  ; 
but  then  the  spectra  of  these  elements,  so  abundant  on  the 


RELATIONS  OF  THE  ATOMS  TO  LIGHT.  187 

earth's  surface,  are  so  much  feebler  than  those  of  the  metals, 
that  it  is  doubtful  whether  the  negative  evidence  of  the  spec- 
troscope is  trustworthy  in  these  cases. 

The  elements  thus  recognized  in  the  sun  only  account  for  a 
small  portion  of  the  dark  lines,  and  the  scheme  of  the  chemical 
elements  is  apparently  so  incomplete  on  the  earth,  at  least  so 
far  as  we  know  it  (103),  that  we  should  not  be  surprised  to 
find  a  multitude  of  new  forms  of  elementary  matter  at  the  cen- 
tre of  the  solar  system.  But,  on  the  other  hand,  the  meteorites 
have  brought  to  us  no  new  elements,  and  their  evidence,  there- 
fore, as  far  as  it  goes,  is  adverse  to  the  assumption  that  there 
exists  in  the  sun's  atmosphere  such  a  great  number  of  unknown 
elements  as  the  dark  lines  would  indicate,  and  this  obvious  ex- 
planation of  their  vast  number  cannot  be  regarded  as  probable. 

If  next  we  turn  the  spectroscope  on  some  of  the  brighter 
fixed  stars,  we  shall  see  continuous  spectra  like  the  solar 
spectrum,  of  greater  or  less  extent,  and  covered  by  dark  lines. 
A  careful  comparison  of  these  lines  would  seem  to  indicate 
that  the  stars  differ  very  greatly  from  each  other,  although  in 
general  they  are  bodies  similar  to  our  sun ;  and  if  our  theory 
is  correct,  we  have  been  able  to  detect  the  presence  of  sodium, 
magnesium,  hydrogen,  calcium,  iron,  bismuth,  tellurium, 
antimony,  and  mercury  in  Aldebaran,  and  other  elements  in 
other  stars. 

The  most  remarkable  result  of  stellar  chemistry  remains  yet 
to  be  noticed.  On  examining  the  nebulas  with  the  spectro- 
scope, it  has  been  found  that  while  some  of  them  show  a  con- 
tinuous spectrum,  there  are  a  number  of  these  remarkable 
bodies  which  exhibit  the  phenomena  of  bright  lines.  This 
would  lead  us  to  the  conclusion  that  the  last  are  really,  as  the 
nebular  theory  assumes,  masses  of  incandescent  gas,  while  the 
first  are  not  true  nebula,  but  simply  clusters  of  very  distant 
stars.  An  examination  of  the  comets  has  confirmed  the  pre- 
vious conclusion  that  they  also  are  mere  masses  of  gas,  but, 
singularly  enough,  the  light  from  the  coma  of  one  of  those 
bodies  gave  a  continuous  spectrum,  due  probably  to  reflected 
sunlight. 

98.  Absorption  Spectra.  — When  a  luminous  flame  is  viewed 
with  a  spectroscope  through  a  solution  of  any  salt  of  the 
metal  Erbium,  the  otherwise  continuous  spectrum  of  the  flame 


188  RELATIONS  OF  THE  ATOMS  TO  LIGHT. 

is  seen  to  be  interrupted  by  several  broad  bands,  which  have  a 
definite  position,  and  are  a  valuable  means  of  recognizing  the 
presence  of  this  very  rare  element.  This  absorption  spectrum, 
as  it  is  called,  is  simply  the  reverse,  the  "  negative  "  of  the 
luminous  spectrum  of  the  same  element. 

In  like  manner  the  salts  of  Didymium  give  an  equally 
characteristic,  although  very  different,  absorption  spectrum, 
which  is  in  fact  the  only  sure  test  we  possess  for  this  remark- 
able elementary  substance  ;  and  as  the  bands  may  under  some 
conditions  be  seen  with  reflected,  as  well  as  with  transmitted 
light,  we  may  apply  the  test  even  to  opaque  solids.  Also,  the 
same  absorption  bands  are  obtained  either  when  the  light  is 
transmitted  through  a  liquid  solution,  or  through  a  solid  crystal 
of  any  salt  of  the  metal ;  and,  moreover,  the  incandescent  vapor 
of  the  metal  shows  bright  bands  corresponding  to  the  dark 
bands  in  position.  These  facts  would  seem  to  show  that  the 
characteristic  spectrum  bands  of  an  element  may  be,  at  least 
to  some  extent,  independent  both  of  the  state  of  aggregation, 
and  of  the  condition  of  combination  of  the  elementary  atoms. 

Many  substances  besides  the  compounds  of  the  elements 
just  noticed,  give  characteristic  absorption  spectra  which  have 
been  found  to  be  useful  chemical  tests,  especially  in  the  case 
of  blood,  and  certain  other  bodies  of  organic  origin.  The 
most  remarkable  phenomena  of  this  class  are  the  absorption 
spectra  which  are  seen  when  a  luminous  flame  is  viewed  with 
a  spectroscope  through  various  colored  vapors,  such  as  those 
of  nitric  per-oxide,  bromine,  and  iodine.  The  dark  bands  are 
then  very  numerous,  and  in  some  cases  may  be  resolved  into 
well-defined  lines.  Indeed,  the  absorption  bands  are  a  class  of 
phenomena  closely  allied  to  the  Fraunhofer  lines,  many  of 
which  are  known  to  result  from  the  absorption  by  the  earth's 
atmosphere  of  solar  rays  of  certain  degrees  of  refrangibility : 
and  all  these  facts,  with  many  others,  prove  that  gases  and 
vapors  may  exert  their  peculiar  power  of  elective  absorption 
at  the  ordinary  temperature,  as  well  as  when  incandescent. 
As  a  general  rule,  however,  the  absorption  bands  are  not,  like 
the  bright  lines  of  the  metallic  spectra  or  their  representatives 
among  the  dark  lines  of  the  solar  spectrum,  definite  images  of 
the  slit,  but  they  are  darker  portions  of  the  spectrum  more  or 
less  regularly  shaded,  and  correspond  to  the  broad  bands  or 


RELATIONS   OF  THE   ATOMS   TO  LIGHT.  189 

luminous  spaces  in  the  spectra  of  the  metallic  vapors  when 
not  intensely  heated.  In  each  case  the  effect  results  from  the 
blending  of  a  greater  or  less  number  of  images  of  the  slit, 
differing  in  relative  position  and  intensity. 

99.  Theory  of  Exchanges.  —  The  facts  of  the  two  last 
sections  are  all  illustrations  of  a  general  principle  already 
referred  to  in  connection  with  the  reversal  of  the  sodium 
spectrum.  This  principle  is  known  as  the  "  Theory  of  Ex- 
changes," and  has  been  stated  as  follows :  "  The  relation 
between  the  power  of  emission,  and  power  of  absorption 
for  each  kind  of  rays  (light  or  heat)  is  the  same  for  all 
bodies  at  the  same  temperature."  .  .  .  .  "  Let  R  denote  the 
intensity  of  radiation  of  a  particle  for  a  given  description  of 
light  at  a  given  temperature,  and  let  A  denote  the  proportion 
of  rays  of  this  description  incident  on  the  particle  which  it 
absorbs ;  then  R-7-A  has  the  same  value  for  all  bodies  at  the 
same  temperature,  —  that  is  to  say,  this  quotient  is  a  function 
of  the  temperature  only." 

The  law  of  exchanges  finds  its  widest  application  in  the 
phenomena  of  radiant  heat,  and  so  far  as  experiments  have 
been  made,  it  appears  to  be  true  in  its  greatest  generality.  In 
applying  it  to  explain  the  reversal  of  the  spectra  of  colored 
flames,  we  have  only  to  deal  with  a  single  body  in  its  relations 
to  rays  of  different  qualities.  If  the  principle  is  true,  the 
absorbing  power  of  such  a  body  at  a  given  temperature  must 
bear  a  fixed  ratio  to  its  power  of  emission  for  each  kind  of 
ray.  If,  for  example,  it  has  a  great  power  of  emitting  certain 
rays  of  red  light,  it  has  a  proportionally  great  power  of 
absorbing  the  same  rays.  If,  again,  it  has  a  feeble  power  of 
emitting  violet  rays  of  definite  quality,  its  power  of  absorbing 
such  rays  is  proportionally  feeble,  and  bears  the  same  ratio  to 
the  power  of  emission  as  before  ;  and,  lastly,  it  has  no  power 
of  absorption  over  such  rays  as  it  does  not  itself  emit.  More- 
over, it  would  follow  that,  although  the  relation  of  the  absorb- 
ing to  the  radiating  power  might  vary  very  greatly,  so  that,, 
as  the  temperature  falls,  the  last  may  become  inconsiderable 
as  compared  with  the  first,  or  even  vanish,  no  essential  change 
in  the  character  of  the  elective  absorption  would  be  thus  in- 
duced. Hence,  we  should  expect  that  bodies  would  absorb 
when  cold  rays  of  the  same  quality  which  they  emit  when  hot,. 


190  RELATIONS  OF  THE  ATOMS  TO  LIGHT 

and  also  that  opaque  solids  when  heated  would  emit  white 
light.  We  have  seen  that  the  general  order  of  the  phenomena 
is  that  which  the  law  of  exchanges  would  predict,  and  here,  for 
the  present,  our  knowledge  stops.  We  have  as  yet  been  able 
to  form  no  satisfactory  theory  in  regard  to  the  relations  of  the 
molecular  structure  of  bodies  to  the  medium  through  which  the 
waves  of  light  or  heat  are  transmitted.  It  is,  however, 
worthy  of  notice  that  Euler,  one  of  the  earliest  and  ablest 
investigators  of  undulatory  motion,  predicted  the  discovery  of 
the  law  of  exchanges,  in  assuming  as  a  fundamental  principle  of 
the  undulatory  theory  that  a  body  can  only  absorb  oscillations 
isochronous  with  those  of  which  it  is  itself  susceptible. 

100.  General  Conclusions.  —  The  facts  that  have  been 
stated  in  this  chapter  are  sufficient  to  show,  that,  although  yet 
in  its  infancy,  spectrum  analysis  promises  to  be  one  of  the 
most  powerful  instruments  of  investigation  ever  applied  in 
physical  science.  It  seems  to  be  the  key  which  will  in  time 
open  to  our  view  the  molecular  structure  of  matter ;  and  even 
now  the  results  actually  obtained  suggest  speculations  in 
regard  to  the  ultimate  constitution  of  matter,  of  the  most 
interesting  character.  The  several  monochromatic  rays  which 
the  atoms  of  the  elements  emit,  must  receive  their  peculiar 
character  from  some  motion  in  the  atoms  themselves  which  is 
isochronous  with  the  motion  they  impart.  Is  it  not  then  in 
this  motion  that  the  individuality  of  the  element  resides,  and 
may  not  all  matter  be  alike  in  its  ultimate  essence?  Such 
speculations,  however  wild,  are  not  wholly  unprofitable,  if  only 
they  stimulate  investigation  and  thus  lead  to  further  dis- 
coveries. 


CHAPTER    XVII. 

CHEMICAL    CLASSIFICATION. 

101.  General  Principles.  —  The  glimpses  that  we  have  been 
able  to  gain  of  the  order  in  the  constitution  of  matter  give  us 
grounds  for  believing  that  there  is  a  unity  of  plan  pervading 
the  whole  scheme,  and  encourage  a  confident  expectation  that 
hereafter,  when  our  knowledge  becomes  more  complete,  chem- 
ists may  attain  to  at  least  such  a  partial  conception  of  this 
plan  as  will  enable  them  to  classify  their  compounds  under 
some  natural  system ;  and  in  imagination  we  may  even  look 
forward  to  the  time  when  science  will  be  able  to  express  all 
the  possibilities  of  this  scheme  with  a  few  general  formulae, 
which  will  enable  the  chemist  to  predict  with  absolute  cer- 
tainty the  qualities  and  relations  of  any  given  combination  of 
materials  or  conditions.  But  although  to  a  very  slight  extent 
the  idea  has  been  realized  for  a  small  class  of  the  compounds 
of  carbon,  yet  as  a  whole  this  grand  conception  is  as  yet  but  a 
dream.  The  more  advanced  student  will  find  that  in  limited 
portions  of  some  few  fields  of  investigation  a  fragmentary  clas- 
sification is  possible,  as  in  mineralogy ;  but,  when  he  attempts 
to  comprehend  the  whole  domain,  he  becomes  painfully  aware 
of  the  immense  deficiencies  of  his  knowledge ;  he  is  confused 
by  the  numerous  chains  of  relationship,  which  he  follows,  with 
no  result,  to  sudden  breaks,  and  soon  becomes  convinced  that 
all  such  efforts  must  be  fruitless  until  more  of  the  missing  links 
are  supplied. 

The  best  that  can  now  be  done  in  an  elementary  treatise  on 
chemistry  is  to  group  together  the  elements,  or,  rather,  the 
elementary  atoms,  in  such  families  as  will  best  show  their 
natural  affinities ;  and  then  to  study,  under  the  head  of  each 
element,  the  more  important  and  characteristic  of  its  com- 
pounds. However  little  value  such  a  classification  may  have 
in  its  scientific  aspect,  it  will  bring  together,  to  a  greater  or  less 
extent,  the  allied  facts  of  the  science,  and  thus  will  help  the 
mind  to  retain  them  in  the  memory. 


192  CHEMICAL  CLASSIFICATION. 

In  classifying  the  elementary  atoms,  the  three  most  impor- 
tant characters  to  be  observed  are  the  Prevailing  Quantivalence, 
the  Electrical  Affinities,  and  the  Crystalline  Relations.  The 
first  of  these  characters  serves  more  particularly  to  classify  the 
elements  in  groups,  the  second  to  determine  their  position  in 
the  groups,  and  the  last  to  control  the  indications  of  the  other 
two. 

The  crystalline  relations  of  the  atoms  can  only  be  deter- 
mined by  comparing  the  crystalline  forms  of  allied  compounds, 
and  involve  the  principles  of  isomorphism  already  discussed. 
Moreover,  in  order  to  reach  the  most  satisfactory  scheme  of 
classification,  we  must  take  into  consideration  other  properties 
of  these  compounds  besides  the  crystalline  form;  which,  al- 
though they  may  not  be  so  precisely  formulated,  are  frequently 
important  aids  in  forming  correct  opinions  as  to  the  relations  of 
the  atoms.  It  will  also  be  evident,  from  what  has  previously 
been  stated,  that  more  trustworthy  inferences  as  to  these  rela- 
tions may  frequently  be  drawn  from  the  crystalline  form  and 
properties  of  allied  compounds  than  from  those  of  the  element- 
ary substances  themselves ;  for,  in  addition  to  the  fact  that  so 
many  of  these  substances  crystallize  in  the  isometric  system, 
whose  dimensions  admit  of  no  variation,  it  is  also  true  that,  in 
our  ignorance  of  the  molecular  constitution  of  most  of  them,  we 
often  have  more  certainty,  in  the  case  of  compounds,  that  our 
comparisons  are  made  under  identical  molecular  conditions. 

102.  Metallic  and  Non-Metallic  Elements. —  In  all  works  on 
chemistry  since  the  time  of  Lavoisier,  the  elementary  sub- 
stances have  been  divided  into  two  great  classes,  —  the  metals 
and  the  non-metals ;  and  the  distinction  is  undoubtedly  funda- 
mental, although  too  much  importance  has  been  frequently 
attached  to  the  accident  of  a  brilliant  lustre.  The  character- 
istic qualities  of  a  metal,  with  which  every  one  is  more  or  less 
familiar,  are  the  so-called  metallic  lustre,  that  peculiar  adapt- 
ability of  molecular  structure  known  as  malleability  or  ductility, 
and  the  power  of  conducting  electricity  or  heat.  These  qualities 
are  found  united  and  in  their  perfection  only  in  the  true  metals, 
although  one  or  even  two  of  them  are  well  developed  in  several 
elementary  substances  which,  on  account  of  their  chemical 
qualities,  are  now  almost  invariably  classed  with  the  non- 
metals,  —  as,  for  example,  in  selenium,  -tellurium,  arsenic, 


CHEMICAL  CLASSIFICATION.  193 

antimony,  boron,  and  silicon.  Besides  the  properties  above 
named,  many  persons  also  associate  with  the  idea  of  a  metal  a 
high  specific  gravity ;  but  this  property,  though  common  to  most 
of  the  useful  metals,  is  by  no  means  universal ;  and,  among  the 
metals  with  which  the  chemist  is  familiar,  we  find  the  lightest, 
as  well  as  the  heaviest,  of  solids.  The  non-metallic  elements, 
as  the  name  denotes,  are  distinguished  by  the  absence  of  metal- 
lic qualities  ;  but  the  one  class  merges  into  the  other. 

The  presence  or  absence  of  metallic  qualities  in  the  ele- 
mentary substances  is  for  some  unknown  reason  intimately 
associated  with  the  electrical  relations  of  their  atoms,  —  those  of 
the  metals  being  electro-positive,  while  those  of  the  non- 
metals  are  electro-negative,  with  reference,  in  each  case,  to  the 
atoms  of  the  opposite  class.  In  the  classification  given  in 
Table  II.  we  have  associated  together  in  the  same  family  both 
the  metals  and  the  non-metals  having  the  same  quantivalence, 
believing  that  such  an  arrangement  not  only  best  exhibits  the 
relations  of  the  atoms,  but  also  that  in  a  course  of  elementary 
instruction  it  presents  the  facts  of  chemistry  in  the  most  logical 
order. 

103.  Scheme  of  Classification.  —  The  classification  of  the 
elementary  atoms  which  has  been  adopted  in  this  book  is  shown 
in  Table  II. 

In  the  first  place  the  atoms  are  divided  into  two  large 
families,  the  Perissads  and  the  Artiads  (27). 

Secondly,  these  families  are  subdivided  into  groups  (separated 
by  bars  in  the  table)  of  closely  allied  elements.  The  atoms  of  any 
one  of  these  groups  are  isomorphous ;  and  they  are  arranged 
in  the  order  of  their  weights,  which  is  found  to  correspond  also, 
in  almost  every  case,  to  their  electrical  relations.  Each  group 
forms  a  very  limited  chemical  series ;  and  not  only  the  weights 
and  the  electrical  relations  of  the  atoms,  but  also  many  of  the 
physical  qualities  of  the  elementary  substances,  vary  regularly 
as  we  pass  from  one  end  of  the  series  to  the  other.  The  order 
of  the  variation,  however,  is  not  always  the  same  ;  for  while  in 
some  cases  the  lightest  atoms  of  a  series  are  the  most  electro- 
negative, in  other  cases  they  are  the  most  electro-positive. 

Thirdly,  in  arranging  the  groups  of  allied  atoms  we  have 
followed  the  prevailing  quantivalence  of  the  group,  and  those 
groups  whose  elementary  atoms  exhibit  in  general  the  lowest 


194  CHEMICAL  CLASSIFICATION. 

quantivalence  are,  as  a  rule,  placed  first  in  order;  but  with 
our  present  limited  knowledge  there  must  be  some  uncertainty 
in  regard  to  the  details  of  such  an  arrangement,  and  the  prin- 
ciple has  sometimes  been  violated  so  as  to  bring  together  those 
groups  of  atoms  which  are  most  allied  in  their  chemical  rela- 
tions. 

The  remarks  already  made  in  regard  to  the  general  scheme 
of  chemical  classification  apply  with  almost  equal  force  to  the 
partial  system  here  attempted.  The  very  attempt  makes  evi- 
dent the  fragmentary  character  of  our  knowledge,  even  in  re- 
gard to  the  exceedingly  limited  portion  of  the  subject  with 
which  we  are  dealing.  The  idea  of  classification  by  series  was 
first  developed  in  the  study  of  organic  chemistry,  where  the 
principle  is  much  more  conspicuous  than  among  inorganic  com- 
pounds. Thus,  as  has  been  shown  (40),  we  are  acquainted 
with  twenty  acids  resembling  acetic  acid,  which  form  a  series 
begirining  with  formic  acid  and  ending  with'  melissic  acid.  Each 
member  of  this  series  differs  in  composition  from  the  preceding 
member  by  Cff&  or  by  some  multiple  of  this  symbol ;  and  the 
properties  of  the  compounds  vary  regularly  between  the  extreme 
limits,  according  to  well-established  laws.  Moreover,  many 
other  similar,  although  more  limited,  series  of  compounds  are 
known,  and  the  principle  realized  in  these  organic  series  seems 
to  be  the  true  idea  of  all  chemical  classification.  But,  in  attempt- 
ing to  apply  it  to  the  chemical  elements,  we  find  only  two  or  three 
groups  of  atoms  where  the  series  is  of  sufficient  extent  to  make 
the  relations  of  the  members  evident.  In  most  cases  it  would 
seem  as  if  we  only  knew  one  or  two  members  of  a  series,  and 
this  apparent  ignorance  not  only  throws  doubt  on  the  general 
application  of  our  principle,  but  also  renders  uncertain  the  details 
of  our  scheme,  even  assuming  that  the  principle  of  the  classi- 
fication is  correct.  Hence,  also,  great  differences  of  opinion 
may  be  reasonably  entertained  in  regard  to  the  position  which 
the  different  atoms  ought  to  occupy  in  such  a  scheme. 

Another  very  important  cause  of  uncertainty  in  any  scheme 
of  classifying  the  elements  arises  from  the  double  relationships 
which  many  of  them  manifest.  Thus  iron,  which  we  have 
associated  with  manganese  and  aluminum,  is  in  some  of  its 
relations  closely  allied  to  magnesium  and  zinc.  Many  other 
elements  resemble  iron  in  having  a  similar  two-fold  character, 


CHEMICAL  CLASSIFICATION.  195 

and  different  authors  may  reasonably  assign  to  such  elements 
different  places  in  their  systems  of  classification,  according  as 
they  chiefly  view  them  from  one  or  the  other  aspect.  Hence 
arises  a  degree  of  uncertainty  which  affects  our  whole  system, 
and  cannot  be  avoided  in  the  present  state  of  the  science. 

Indeed,  no  classification  in  independent  groups  can  satisfy 
the  complex  relations  of  the  elements.  These  relations  cannot 
be  represented  by  a  simple  system  of  parallel  series,  but  only 
by  a  web  of  crossing  lines,  in  which  the  same  element  may 
be  represented  as  a  member  of  two  or  more  series  at  once, 
and  as  affiliating  in  different  directions  with  very  different 
classes  of  elements.  In  the  present  fragmentary  state  of  our 
knowledge,  such  a  classification  as  we  have  just  indicated  is 
not  attainable.  The  scheme  adopted  in  this  book  only  indi- 
cates in  each  case  a  single  line  of  relationship  ;  but  we  have 
always  endeavored  to  place  each  element  in  that  relation 
which  is  the  most  characteristic ;  and,  however  imperfect  such 
a  scheme  may  be,  it  will  nevertheless  assist  study  by  bringing 
before  the  student's  mind  the  facts  of  the  science  in  a  syste- 
matic and  natural  order. 

104.  Relations  of  the  Atomic  Weights.  —  If  the  principle  of 
classification  which  we  have  adopted  is  correct,  and  the  ele- 
ments actually  belong  to  series  like  those  of  the  compounds  of 
organic  chemistry,  we  should  naturally  expect  that  the  atomic 
weights  would  conform  to  the  same  serial  law ;  and  it  is  a  re- 
markable fact  that  the  differences  between  the  atomic  weights 
of  the  elements  of  the  same  group  are  in  most  cases  very  nearly 
multiples  of  16.  The  value  of  this  common  difference  varies 
between  15  and  17,  and  we  must  admit  in  some  cases  the 
simplest  fractional  multiples ;  but  the  mean  value  is^  very 
nearly  16,  and  the  frequent  occurrence  of  this  difference  is 
very  striking.  This  numerical  relation  is  not  absolutely  exact, 
but  here,  as  in  the  periods  of  the  planets,  in  the  distribution  of 
leaves  on  the  stem  of  a  plant,  and  in  other  similar  natural 
phenomena,  there  is  a  marked  tendency  towards  a  certain  nu- 
merical result,  which  is  fully  realized,  however,  only  in  com- 
paratively few  cases. 

Other  numerical  relations  which  have  been  noticed  between 
the  atomic  weights  are  probably  only  phases  of  the  same  law 
of  distribution  in  series.  Thus  the  atomic  weight  of  sodium  is 


196  CHEMICAL  CLASSIFICATION. 

very  nearly  the  mean  between  that  of  lithium  and  potassium  ; 
and  the  atomic  weights  of  chlorine,  bromine,  and  iodine,  of  glu- 
cinum,  yttrium  and  erbium,  of  calcium,  strontium,  and  barium, 
of  oxygen,  sulphur,  and  selenium,  are  similarly  related.  Again, 
there  are  several  pairs  of  allied  elements,  between  whose 
atomic  weights  there  is  very  nearly  the  same  difference.  Thus 
the  difference  between  the  atomic  weights  of  indium  and  cad- 
mium is  very  nearly  the  same  as  that  between  the  atomic 
weights  of  magnesium  and  zinc,  and  the  difference  between  the 
atomic  weights  of  niobium  and  tantalum  the  same  as  that  be- 
tween the  atomic  weights  of  molybdenum  and  tungsten.  A 
careful  study  of  the  atomic  weights  will  also  reveal  many  other 
approximate  relations  of  the  same  sort ;  but  although  the 
study  of  these  relations  is  highly  interesting,  and  may  lead  here- 
after to  valuable  results,  yet  no  great  importance  can  be  at- 
tached to  them  in  the  present  state  of  the  science. 


PART   II. 


INTRODUCTION. 

HAVING  developed  in  Part  I.  the  fundamental  principles  of 
chemical  science,  we  shall  next  give,  in  Part  II.,  a  brief  sum- 
mary of  the  more  important  elements  and  compounds,  exhib- 
iting their  constitution  and  relations  by  means  of  formulae  and 
reactions,  and  adding  a  number  of  questions  and  problems, 
which  will  serve  to  direct  the  attention  of  the  student  to  the 
more  important  facts  and  principles,  or  to  those  which,  being 
only  implied  in  the  context,  might  be  otherwise  overlooked, 
and  which  will  also  give  him  the  means  of  testing  the  thor- 
oughness and  accuracy  of  his  knowledge.  The  answers  to  the 
problems  have  been  calculated  with  the  four-place  logarithms, 
which  will  be  found  at  the  end  of  the  volume.  Used  in  con- 
nection with  the  table  of  antilogarithms  which  accompanies 
them,  the  logarithms  give  results  which  are  accurate  to  the 
fourth  significant  figure,  and  this  degree  of  accuracy  exceeds 
in  almost  every  case  that  of  the  experimental  data  given  in 
the  problems.  With  certain  exceptions  referred  to  below,  the 
answers  to  the  questions  are  either  stated  or  implied  in  the 
immediate  context,  or  in  the  sections  and  formulae  to  which 
reference  is  made.  The  references  to  sections  are  enclosed  in 
parentheses,  and  those  to  formulae  in  brackets.  Direct  ques- 
tions on  the  facts  stated  in  the  summary  are  seldom  given,  and 
obviously  would  be  superfluous ;  but  the  student  should  make 
himself  thoroughly  acquainted  with  the  subject-matter  of  each 
section  before  he  attempts  to  answer  the  questions  or  solve  the 
problems  which  follow.  In  studying  the  book,  however,  he 
should  aim  to  acquire  a  knowledge  of  the  general  principles 
and  mutual  relations  which  are  exhibited,  rather  than  to  com- 
mit to  memory  the  isolated  facts.  He  must  never  forget  that 
he  is  dealing,  not  with  abstractions,  but  with  real  things  and 
actual  phenomena,  and  that  chemical  formulae  are  merely  ex- 


200  INTRODUCTION. 

pressions  of  definite  facts  ascertained  by  experiment.  More- 
over, he  must  discriminate  with  the  greatest  care  between  the 
facts  directly  stated  or  expressed  by  the  reactions,  and  the  in- 
ferences drawn  from  them,  and  he  should  be  required  to  state 
clearly  the  successive  steps  in  every  process  of  inductive  rea- 
soning. As  was  stated  in  the  preface,  this  portion  of  the  book 
is  only  intended  as  an  auxiliary  to  lecture-room  or  laboratory 
instruction,  and  the  closer  the  lessons  can  be  connected  with 
the  experimental  illustrations  the  better. 

The  elements  are  studied  in  the  following  chapters  in  the 
order  in  which  they  are  arranged  in  Table  II.,  and  in  connec- 
tion with  each  element  we  describe,  or  at  least  mention,  the 
more  important  compounds  which  it  forms  with  the  elements 
preceding  it  in  our  classification.  At  least  this  is  the  general 
rule,  but,  so  far  as  regards  the  compounds,  we  do  not  follow 
this  order  invariably,  departing  from  it  whenever  it  may  be 
necessary  to  illustrate  the  relations  of  the  element  we  may  be 
studying.  Thus  we  describe  with  each  element  its  chief  oxy- 
gen and  sulphur  compounds  from  the  first.  No  attempt  has 
been  made  to  embrace  the  whole  field,  but  the  aim  has  been  to 
illustrate  fully  the  principles  of  chemical  philosophy,  and  to 
give  a  clear  idea  of  that  phase  of  the  scheme  of  nature  which 
has  been  revealed  by  the  study  of  chemistry.  As  stated  in  the 
Preface,  the  "  Questions  and  Problems  "  are  an  essential  feature 
in  the  plan  of  the  work,  and  serve  to  supplement  as  well  as  to 
illustrate  the  text.  The  student  will  find  that  the  knowledge 
which  he  gains  inferentially,  while  seeking  the  answers  to  the 
questions  or  solving  the  problems,  is  peculiarly  valuable,  and 
the  acquisition  has  something  of  the  zest  of  new  discovery.  As 
he  advances,  he  will  meet  with  questions  which  he  cannot  fully 
answer  without  consulting  more  extended  works,  and  which  are 
intended  to  direct  his  study  beyond  the  limits  of  this  book.  He 
may  consult  in  such  cases  Watts's  Dictionary  of  Chemistry, 
Miller's  Elements  of  Chemistry,  Percy's  Metallurgy,  and  Dana's 
System  of  Mineralogy. 


CHAPTER    XVIII. 

THE  PERISSAD  ELEMENTS. 

Division  I. 

105.  HYDROGEN.    H—  1.  —  Monad.       The  .lightest 
atom,  and  the  standard  of  quantivalence.     Very  widely  diffused 
in  nature.     Forms  one  ninth  of  water,  and  is  a  constituent  of 
almost  all  vegetable  and  animal  substances  as  well  as  of  many 
minerals.    The  essential  constituent  of  all  acids  and  bases,  from 
which  it  is  readily  displaced  by  other  atoms. 

106.  Hydrogen  Gas.  H-H.  —  The  lightest  substance  known 
in  nature.     Sp.  Gr.  =  1,  the  standard  of  comparison.     Seldom 
found  in  a  free  state  in  nature.     Best  prepared  by  the  action  of 
zinc  or  iron  on  dilute  sulphuric  acid. 

Zll  +  (J2JS04  +  Aq)  =  (ZnSOt  +  Aq)  +  HI-SI.    [64] 

Very  combustible.  Has  the  greatest  calorific  power  of  any 
substance  known.  Aqueous  vapor  sole  product  of  its  com- 
bustion. 

2m-in  +  ©<o>  =  2m2©.  [65] 

107.  Hydric  Oxide  (Water}.    H.,0.  —  The  universally  dif- 
fused liquid  of  the  globe.     The  life-blood  of  nature,  and  the 
chief  constituent  of  organized  beings.     Below  0°  a  crystalline 
solid  (hexagonal  system,  Figs.  14  and  16).     Sp.  Gr.  =  0.918. 
Under  the  ordinary  pressure  of  the  air  it  boils  at  100°,  but 
exists  in  the  atmosphere  in  the  state  of  vapor,  at  all  temper- 
atures.    For  maximum  tension  of  vapor  at  different  temper- 
atures see  Chem.  Phys.  (284  and  312).     Water  is  an  almost 
universal  solvent  and  the  medium  of  most  chemical  changes. 
Its  molecular  structure  is  regarded  as   the   type   of  a  very 
large  class  of  chemical  compounds.     Its  composition  may  be 
determined,  —  First,  by  electrolysis  (91  and  [65]  reversed). 

9* 


202  HYDROGEN.  [§  108. 

Secondly,  by  passing  a  mixture  of  steam  and  chlorine  gas 
through  a  red-hot  tube. 


2IH2(Q>  +  2O1-O1  =  45HO1  -f  ©=©.  [66] 

Thirdly,  by  exploding  in  an  eudiometer-tube  a  mixture  of  oxy- 
gen and  hydrogen  gas  [65].  Fourthly,  by  passing  hydrogen 
gas  over  heated  cupric  oxide. 

CuO  +  SHU  =  Cu  +  HI,©.  [67] 

Water  combines  with  anhydrides  to  form  acids,  as 


t,  r681 

or  P2  05  +  3H20  =  2fff  OfPO. 

It  combines  with  metallic  oxides  to  form  hydrates,  bases,  or 
alkalies,  as 


CaO-\-H20=Ca=02=H2.  [63] 
It  combines  with  many  salts  as  water  of  crystallization,  as 
Fe=S04  .  7H20  Cryst.  Ferrous  Sulphate. 

108.  Hydroxyl.  HO.  —  An  important  compound  radical, 
which  may  be  regarded  as  a  factor  (28)  in  the  molecules  of 
many  chemical  compounds,  and  for  this  reason  it  is  sometimes 
convenient  to  write  its  symbol  Ho  (22).  The  oxygen  bases 
may  be  considered  as  compounds  of  hydroxyl  with  electro-posi- 
tive atoms  or  radicals,  and  the  oxygen  acids  as  compounds  of 
the  same  with  electro-negative  atoms  or  radicals.  Thus  we 
may  write  the  symbols  of  the  following  compounds  as  shown 
below :  — 

Na-Ho, 

fe 

[70] 


Sodic  Hydrate 
Baric  Hydrate 
Ferric  Hydrate 

Na-O-H 
Ba-OfH, 

or 

« 

u 

Nitric  Acid 
Sulphuric  Acid 
Phosphoric  Acid 

H-0-NOZ 

u 

a 

109.   Hydric Peroxide  (Oxygenated  Water).  Jf202orffo-ffo. 


§  109.]  QUESTIONS  AND  PROBLEMS.  203 

—  Best  regarded  as  the  "radical  substance"  (22  and  69) 
corresponding  to  hydroxyl.  In  its  most  concentrated  form  it  is 
a  colorless  liquid  of  the  consistency  of  syrup,  and  having  a  de- 
cided odor  resembling  chlorine.  Soluble  in  water  in  all  pro- 
portions. Prepared  by  action  of  carbonic  acid  on  baric  peroxide. 

BaO2  +  (ff2C03  +  Aq)  =  BaCO*  +  (ff2O2  +  Aq).  [71] 

Carbonic  anhydride  is  passed  through  water  in  which  Ba  0%  is 
suspended  and  the  solution  of  Jf2  02  subsequently  evaporated  in 
vacuo.  Decomposed  by  fine  metallic  powders,  and  also  spon- 
taneously at  temperatures  higher  than  22°,  into  water  and  oxy- 
gen gas. 

(2ff202  +  Aq)  =  (2ff20  +  Aq)  +  (SXD.        [72] 
It  liberates  iodine  from  its  compounds. 

2KI+  (Ho-Ho  +  Aq)  =  I-I  +  (ZK-Ho  +  Aq).  [73] 
It  generally  acts  as  an  oxidizing  agent. 

PfoS+  (±ff202  +  Aq)  =  ?k$04  +  (4ff20  +  Aq).  [74] 
It  sometimes,  however,  acts  as  a  reducing  agent. 

[75] 


Questions  and  Problems.1 

1.  What  distinction  can  be  drawn  between  a  chemical  element 
and  an  elementary  substance,  it  being  understood  that  the  word  ele- 
ment is  used  in  a  restricted  sense,  as  applying  only  to  the  ultimate 
atoms  into  which  matter  may  be  resolved  ?     Illustrate  the  distinction 
by  the  case  of  hydrogen.     (69  ;  18  and  22.) 

2.  What  is  the  essential  characteristic  of  an  acid  and  of  a  base  ? 
(35  and  36.) 

3.  What  is  the  ground  for  the  belief  that  each  molecule  of  hydro- 
gen gas  consists  of  two  atoms  ?     (19.) 

1  It  is  assumed  in  all  the  problems  of  this  book  that  the  temperature  is 
0°  C.,  and  the  pressure  76  c.  m.,  unless  otherwise  stated.  The  following 
abbreviations  will  be  used:  c.  m.,  centimetre;  c~m78,  cubic  centimetre; 
d.  m.3,  cubic  decimetre;  kilo.,  kilogrammes,  &c.  (See  Table  I.) 


204  QUESTIONS  AND  PROBLEMS. 

4.  The  litre  and  the  crith,  the  molecular  weight  of  hydrogen  and 
its  molecular  volume,  sustain  what  relation  to  each  other  ?     State  the 
reason  for  the  rule  on  page  49.     (2  and  25.) 

5.  How  many  grammes  of  zinc  and  how  many  of  sulphuric  acid 
will  yield  one  litre  of  hydrogen  gas  ? 

Ans.  2.92  grammes  of  zinc,  and  4.39  grammes  of  sulphuric  acid. 

6.  If  45  grammes  of  zinc  are  used  in  reaction  [64],  how  many 
cubic  centimetres  of  sulphuric  acid  must  be  used  also,  and  how  many 
grammes  of  zincic  sulphate,  and  how  many  litres  of  hydrogen  gas, 
will  be  formed  in  the  process  (Sp.  Gr.  of  HZSO±  =  1.843)  ? 

Ans.  36.7  cTm.3  of  sulphuric  acid,  111.3  grammes  of  zincic  sul- 
phate, and  15.4  litres  of  hydrogen. 

7.  What  volume  of  water  should  be  mixed  with  the  sulphuric  acid 
in  the  last  problem,  assuming  that  the  reaction  takes  pkce  at  20°, 
and  that  100  parts  of  water  at  that  temperature  will  dissolve  53 
parts  of  zincic  sulphate  ? 

Ans.  209.9  cmn3,  or  enough  to  dissolve  all  the  zinc  salt  formed. 

8.  What  weight  of  iron  must  be  used  to  generate  sufficient  hydro- 
gen to  raise  in  the  atmosphere  by  its  buoyancy  a  total  weight  of  121 
grammes  (Sp.  Gr.  of  air  14.5  nearly)  ? 

Ans.  100  litres  of  hydrogen  gas  will  be  required,  and  this  can  be 
made  from  250.9  grammes  of  iron. 

9.  Assuming  that  the  principle  of  (1 7)  is  correct,  why  does  it  fol- 
low from  reaction  [65]  that  the  molecule  of  oxygen  gas  must  contain 
at  least  two  atoms  V 

10.  What  is  the  volume  of  4.480  grammes  of  hydrogen  at  273°.2 
[9]?  Ans.  100  litres. 

11.  What  is  the  volume  of  4.480  grammes  of  hydrogen  at  0°  and 
under  a  pressure  of  38  c.  m.  [4]  ?  Ans.  100  litres. 

12.  A  block  of  ice  weighs  36.72  kilos.     What  is  its  volume  [1]  ? 

Ans.  40  cLln:3 

13.  An  iceberg  is  floating  in  sea  water  (Sp.  Gr.  =  1.028).    What 
proportion  of  its  bulk  is  submerged?  Ans.  0.8932. 

14.  One  kilogramme  of  steam  at  100°  will  melt  how  many  kilos, 
of  ice  ? 

Ans.  The  steam  by  condensing  and  cooling  would  give  out  637 
units  of  heat,  which  is  adequate  to  melt  637-f-79  =  8  + 
kilogrammes  of  ice.  (14  and  16.) 

15.  What  is  the  weight  of  one  litre  of  confined  steam  at  the  tem- 
perature of  144°  ?     Tension  of  steam  at  144°  equals  4  atmospheres. 

Ans.  Weight  of  litre  of  steam  at  0°  and  76  c.  m.  would  be  theo- 
retically 9  criths.  Hence  weight  at  144°  and  4  X  76  c.  m. 
is,  by  [6]  and  [10],  23.58  criths  or  2.113  grammes. 


QUESTIONS  AND  PROBLEMS.  205 

16.  What  is  the  weight  of  one  litre  of  superheated  steam  under 
normal  pressure,  and  at  546°.4  ?  Ans.  0.2688  grammes. 

1 7.  Water  is  forced  into  a  glass  globe  containing  dry  air,  at  the 
temperature  of  100°  C.  and  under  the  normal  pressure,  as  long  as  it 
continues  to  evaporate.     What  will  be  the  tension  of  the  moist  air  ? 

Ans.  Water  or  any  other  liquid  evaporates  into  a  confined  space 
until-  the  vapor  attains  its  maximum  tension  for  the  existing 
temperature,  even  when  the  space  is  filled  with  another  gas ; 
and  the  tension  of  the  mixture  of  gas  and  vapor  is  equal  to 
the  sum  of  the  tension  which  each  would  exert  separately. 
Chem.  Phys.  (312).  The  maximum  tension  of  aqueous 
vapor  at  100°  is  76  c.  m.,  and  hence  the  tension  of  the  nioist 
air  in  the  globe  must  be  152  c.  m. 

18.  A  volume  of  hydrogen  gas  standing  in  a  bell-glass  over  a 
pneumatic  trough,  and  consequently  saturated  with  moisture,  meas- 
ures 100  cTm:3.     The  temperature  is  22°. 3  and  pressure  on  the  gas 
76  c.  m.     What  would  be  the  volume  under  the  same  conditions  if 
the  air  were  perfectly  dry  ? 

Ans.  The  maximum  tension  of  aqueous  vapor  at  given  temper- 
ature is  2  c.  m.  Hence  if  vapor  were  removed,  the  tension 
of  the  gas  would  become  74  c.  m.,  provided  the  volume  re- 
mained constant.  But  the  exterior  pressure  being  76  c.  m., 
the  volume  must  accommodate  itself  to  this  condition,  and 
hence  by  [4]  would  be  reduced  to  97.36  c.  m. 

19.  What  is  the  Sp.  Gr.  of  aqueous  vapor?     What  is  meant  by 
the  term  Sp.  Gr.  as  applied  to  a  vapor,  and  under  what  conditions  is 
it  assumed  to  be  taken  ?     (1  and  17.)  Ans.  9. 

20.  In  Table  III.  the  weight  of  one  litre  of  aqueous  vapor  under 
the  standard  conditions  of  temperature  and  pressure  is  given  as  9 
criths.     AVhy  is  this  value  a  fiction  ?  and  why  is  an  impossible  value 
given  in  the  table  ?     Chem.  Phys.  (329). 

21.  In  the  experiment  indicated  by  reaction  [66]  the  oxygen  gas 
was  collected  in  a  bell-glass  over  water.     It  measured  1,101  c.  m.3 
at  the  temperature  22°.3  and  under  a  pressure  of  76  c.  m.     What 
was  the  volume  of  chlorine  gas  used,  measured  under  the  normal 
conditions  ?     The  tension  of  aqueous  vapor  at  22°.3  is  2  c.  m. 

Ans.  2  litres. 

22.  How  much  copper  will  be  reduced  in  the  formation  of  nine 
grammes  of  water,  and  what  volume  of  hydrogen  gas  will  be  used  in 
the  reaction  ? 

Ans.  31.7  grammes  of  copper  and  11.16  litres  of  hydrogen. 

23.  It  has  been  found  by  exact  experiments  that  for  every  nine 


206  QUESTIONS  AND  PROBLEMS. 

grammes  of  water  formed  by  reaction  [6  7]  the  cupric  oxide  lost  in 
weight  eight  grammes.  What  is  the  percentage  composition  of 
water?  Ans.  11.112  of  hydrogen  and  88.888  of  oxygen. 

24.  Given  percentage  composition  of  water  and  the  Sp.  Gr.  of 
aqueous  vapor,  and  assuming  that  the  molecule  of  water  contains 
only  one  oxygen  atom,  how  can  you  deduce  the  atomic  weight  of 
oxygen  ?     (23.) 

25.  Assuming  that  all  the  heat  of  combustion  is  utilized,  how 
many  litres  of  hydrogen  must  be  burnt  to  convert  into  free  steam 
one  kilogramme  of  boiling  water,  and  how  does  the  volume  of  steam 
generated  compare  with  the  volume  of  gas  burnt  ? 

Ans.  176.8  litres  of  hydrogen  gas  and  1,240  litres  of  steam,  when 
reduced  to  standard  conditions.  (14  and  17.)  (61.) 

26.  Assuming  that  all  the  heat  of  combustion  is  retained  in  the 
aqueous  vapor  formed  from  the  burnt  hydrogen,  how  will  the  vol- 
ume of  the  expanded  vapor  compare  with  that  of  the  gas  consumed  ? 

Ans.  By  problem  on  page  121  it  appears  that  the  temperature  of 
the  vapor  would  be,  under  the  conditions  assumed,  6,853°. 
Hence  the  volume  would  be  26.08  times  as  great  as  that  of 
the  gas  [9]. 

27.  Assuming  that  the  whole  volume  of  gas  resulting  from  the 
electrolysis  of  water  is  retained  in  the  space  previously  occupied  by 
the  water,  what  would  be  its  tension?       Ans.  1,860  atmospheres. 

28.  What  is  the  relation  of  an  anhydride  to  an  acid,  or  of  a  me- 
tallic oxide  to  a  hydrate  ?     (37  and  47.) 

29.  What  objections  may  be  raised  to  the  method  of  writing  the 
symbols  of  acids  and  bases  used  in  [70]  ? 

30.  What  is  the  distinction  between  a  compound  radical  and  a 
radical  substance  ? 

31.  Why  does  reaction  [73]  sustain  the  view  that  hydric  perox- 
ide contains  the  radical  hydroxyl?     Do  not  reactions  [72],  [74], 
and  [75]  point  to  another  view  of  its  constitution? 

32.  Analyze  reaction  [75],  and  show  that  it  is  in  harmony  with 
the  modern  theory  of  the  constitution  of  the  oxygen  moleculel 


§113.]  FLUORINE.  —  CHLORINE.  207 


Division  H. 

110.  FLUORINE.  ^=19.  —  Quantivalence  usually  one, 
but  its  atomicity  is  probably  of  higher  order.     A  chief  constit- 
uent of  fluor-spar,  CaF^  and  of  cryolite,  Na^Al^F-^.    Found  also, 
but  in  small  quantities,  in  Apatite,  Tourmaline,  Mica,  and  a  few 
other  minerals.     Also  in  the  bones  of  animals,  especially  in  the 
teeth.     The  elementary  substance  F-F  is  undoubtedly  a  gas, 
but  it  has  not  with  certainty  been  isolated. 

111.  Hydrofluoric  Acid.     HF.  —  The  anhydrous  acid  is  at 
15°  a  colorless  mobile  liquid,  extremely  volatile,  boiling  at  19.5°, 
densely  fuming  in  the  air,  and  attracting  greedily  water  from 
the  atmosphere.     It  is  exceedingly  corrosive,  and  a  highly  dan- 
gerous substance,     The  dilute  acid  is  obtained  by  distilKng  a 
mixture  of  powdered  fluor-spar  and  sulphuric  acid  in  a  plati- 
num or  lead  retort. 


CaF2  +  (H.SO,  +  Aq)  =  CaSO4  +  2H3I?  +  ^q.  [76] 

Cryolite  may  be  used  advantageously  instead  of  fluor-spar. 
This  acid  is  distinguished  for  its  power  of  dissolving  silica,  with 
which  it  forms  volatile  products.  Hence  it  is  much  used  in 
chemical  analysis  for  decomposing  siliceous  minerals,  and  in  the 
arts  for  etching  glass. 

112.  CHLORINE.  01=  35.5.  —  Quantivalence  usually  one, 
but  atomicity  probably  of  a  higher  order.     Very  widely  dis- 
tributed in  nature,  chiefly  in  combination  with  sodium,  forming 
common  salt. 

113.  Chlorine  Gas.    Cl-Cl.  —  Yellowish-green   gas,   which 
may  be  liquefied  by  pressure,  but  has  never  been  frozen.     Sol- 
uble in  water,  with  which  it  forms  at  0°  a  crystalline  hydrate. 
Highly  corrosive,  and  enters  into  direct  union  with  most  of  the 
elementary  substances.     Discharges  vegetable  colors  and  de- 
stroys noxious  effluvias,  and  hence  much  used  in  the  arts  as  a 
bleaching  and  disinfecting  agent.       Best  prepared  by  gently 
heating  in  a  glass  flask  a  mixture  of  hydrochloric  acid  and  man- 
ganic dioxide. 


Aq)  = 
(MnCl2  +  2H.O  +  Aq)  +  01-®!.  [77] 

Chlorine  gas  is  a  very  important  chemical  reagent.     It  not 


208 


CHLORINE. 


[§  114. 


only  converts  many  simple  chlorides  into  perchlorides,  but,  with 
the  intervention  of  water  or  of  some  other  oxygen  compound, 
it  also  acts  as  an  oxidizing  agent,  and  to  this  effect  its  bleaching 
power  is  probably  in  great  measure  owing. 


(Sn  C12  +  C12  +  Aq)  =  (Sn  C14  +  Aq). 


[78] 


3  Co-(HO)2  +  (  Cl-  Cl  +  Aq)  = 
[Co2]!(HO)6 


(CoCl2  +  Aq).  [79] 


Chlorine  has  also  a  remarkable  power  of  replacing  hydrogen  in 
many  of  its  compounds.    (31) 

114.  Hydrochloric  Acid.  H~Gl.  —  A  colorless  gas  which 
may  be  liquefied  by  cold  and  pressure,  but  has  not  been  frozen. 
Exceedingly  soluble  in  water,  which  at  4°  absorbs  its  own 
weight  or  about  480  times  its  volume  of  the  gas.  This  solu- 
tion is  very  much  used  in  the  laboratory  as  a  reagent,  and  an 
impure  solution  called  muriatic  acid  is  manufactured  on  a  large 
scale  for  the  uses  of  the  arts.  From  the  Sp.  Gr.  of  the  liquid 
acid  we  can  determine  very  closely  the  quantity  of  gas  held  in 
solution,  by  means  of  tables  in  which  the  results  of  careful  ex- 
perimental determinations  have  been  tabulated.  The  following 
extracts  from  a  table  of  Dr.  Ure's  give  all  the  data  required  for 
calculating  the  problems  in  this  book. 


Sp.  Gr. 
15°  C. 

Per  Cent. 
HCl. 

Sp.  Gr. 
15°  C. 

Per  Cent. 
HCl. 

Sp.  Gr. 
15°  C. 

Per  Cent. 
HCl. 

Sp.  Gr. 

15°  C. 

Per  Cent. 
HCl. 

1.200^ 
1.1893 

40.777 
38.330 

1.1410 
1.1308 

28.544 
26.505 

1.0899 
1.0798 

18.349 
16.310 

1  .0397 
1.0298 

8.155 
6.116 

1.1802 

36.292 

1.1206 

24.466 

1.0697 

14.271 

1.0200 

4.078 

1.1701 

34.252 

1.1102 

22.426 

1.0597 

12.233 

1.0100 

2.039 

1.1599 

32.213 

1.1000 

20.388 

1.0497 

10.194 

1.0060 

1.124 

Muriatic  acid  is  prepared  by  heating  common  salt  with  sul- 
phuric acid  in  large  iron  retorts,  and  conducting  the  gas  formed 
into  large  glass  vessels  containing  water. 

2Na  a  +  H2S04  =  Na2SOt  +  2  SIOI.  [80] 

When  we  make  pure  hydrochloric  acid  in  the  laboratory,  we 
only  use  half  as  much  salt.  The  gas  is  then  given  off  at  a 
much  lower  temperature,  and  glass  retorts  may  be  employed. 

[81] 


§  116.]  CHLORINE.  209 

Hydrochloric  acid  may  also  be  obtained  by  directly  uniting 
hydrogen  and  chlorine  gas. 


+  ®i-oi  =  2nm  [82] 

By  electrolyzing  the  aqueous  solution,  the  last  reaction  is  re- 
versed and  the  acid  is  decomposed.  It  may  also  be  readily 
decomposed  by  metallic  sodium. 

2mOl  +  Na-IVa  =  2NaCl  +  HI-HI.        [83] 

Liquid  hydrochloric  acid  dissolves  most  of  the  metals  and  the 
metallic  oxides,  and  its  uses  in  practical  chemistry  are  illus- 
trated by  the  following  reactions.  See  also  [77]. 

Sll  +  (2ffCl  +  Aq)  =  (SnCl2  +  Aq)  +  HI-HI.   [84] 

ZnO  +  (2HCI  +  Aq)  =  (ZnCl2  +  H20  +  Aq).  [85] 

[Al,]03+  (GffCl  +  Ag)=  ([Al2-]Cl6+3H20  +  Aq).  [86] 


115.  Compounds  of  Chlorine  and  Oxygen.  —  All   of  them 
unstable  and  most  of  them  explosive.     In  regard  to  their  mo- 
lecular constitution  different  views  are  entertained. 

Hypochlorous  Anhydride         C120  Cl-0-d, 

Hypochlorous  Acid  HCIO  H-O-Cl, 

Chlorous  Acid  HC102  ff-0-O-Cl, 

Chlorous  Anhydride  C12  03  Cl-  0-0-  0-  Cl, 

Chloric  Acid  HC103  H-0-O-O-Cl, 

Chloric  Peroxide  C1204  Cl-0-O-O-O-Cl, 

Perchloric  Acid  HC104  H-0-O-O-O-CL 

116.  Potassic  Chlorate.  —  The  most  important  salt  of  any 
of  the  chlorine  oxygen  acids.     Obtained  by  passing  a  stream 
of  chlorine  gas  through  a  warm  solution  of  caustic  potash. 


Aq)  +  3Cl-Cl  = 

(KC103  +  5KCI  +3ff20  +  Aq).  [87] 

Potassic  chlorate,  being  much  the  less  soluble,  is  readily  freed 
from  the  potassic  chloride  by  two  or  three  crystallizations.  It  is 
decomposed  by  heat  alone  into  potassic  chloride  and  oxygen  gas. 

=  2KCI  +  3  (SXD.  [88], 


210  BROMINE.  —  IODINE.  [§117. 

Much  used  for  making  oxygen  gas,  and  also  in  fireworks  and 
the  preparation  of  detonating  powder. 

117.  BROMINE.  Br  =  80.  —  Quantivalence  usually  one, 
but  atomicity  probably  of  a  higher  perissad  order.     Associated 
with  chlorine  in  minute  quantities  in  saline  waters  and  certain 
silver  ores.  The  elementary  substance  (Br-Br}  is  a  very  volatile 
deep-red  liquid.     &p.    Gr.  =  3.187.     Boils  at  63°.     Freezes 
at  7°. 3.     Prepared  from  the  bittern  of  certain  salt  springs,  by 
treating  with  chlorine  and  dissolving  out  the  liberated  bromine 
with  ether. 

118.  IODINE.  1=  127.  —  Quantivalence   and  atomicity 
same  as  with  bromine.     Associated  with  chlorine  in  still  smaller 
quantities  than  bromine.     The  elementary  substance  is  obtained 
from  the  ashes  of  certain  seaweeds.     Crystalline  solid  ;  Sp.  Gr. 
=  4.95.     Melts  at  107°.     Boils  at  175°,  forming  a  dense  violet 
vapor.     Very  slightly  soluble  in  water,  but  is  readily  dissolved 
by  alcohol,  ether,  and  carbonic  sulphide.      Imparts  to  starch 
paste  a  deep  blue  color. 

The  three  elements,  chlorine,  bromine,  and  iodine,  form  a 
well-defined  natural  group,  and  a  careful  comparison  will  show 
that  the  properties  both  of  the  elementary  substances  and  of 
their  compounds  conform  closely  to  the  law  of  progression  which 
marks  a  chemical  series.  These  elements  are  all  highly  electro- 
negative bodies,  but  as  we  descend  in  the  series  we  find  that 
this  character  becomes  less  marked,  and  hence  their  chemical 
energy,  as  manifested  by  the  strength  of  their  affinity  for  ele- 
ments of  the  opposite  class,  such  as  hydrogen  and  the  electro- 
positive metals,  diminishes  as  the  atomic  weight  increases ; 
and  this  law,  as  will  appear,  obtains  with  few  exceptions  in 
all  the  chemical  series.  Moreover,  it  will  also  be  found,  as 
might  indeed  be  anticipated,  that  elements  so  closely  related 
as  these  are  almost  invariably  found  associated  in  nature. 

119.  Characteristic  Reactions.  —  The  soluble  chlorides,  bro- 
mides, and  iodides  all  give,  with  a  solution  of  argentic  nitrate, 
precipitates  insoluble  in  water  and  acids.     The  iodide  of  silver 
may  be  distinguished  from  both  the  chloride  and  the  bromide 
of  the  same  metal  by  its  yellow  color  and  insolubility  in  aqua 
ammonia,  in  which  the  last  two  readily  dissolve.     Bromine  and 
iodine  may  both  be  expelled  from  their  salts  by  chlorine  gas, 
when  the  first  may  be  recognized  by  the  red  color  which  it  im- 


§119.]  QUESTIONS  AND  PROBLEMS.  211 

parts  to  ether  or  chloroform,  and  the  last  by  the  exceedingly 
characteristic  blue  color  which  it  gives  to  starch  paste.  Flu- 
orine is  easily  discovered  because  its  compounds,  when  heated 
in  a  glass  tube  with  potassic  bisulphate,  yield  hydrofluoric  acid 
which  etches  the  glass.  This  element,  although  closely  allied 
to  the  other  three,  differs  so  greatly  in  some  of  its  chemical  re- 
lations that  it  is  doubtful  whether  it  belongs  to  the  same  chem- 
ical series. 


Questions  and  Problems. 

1.  It  appears  that  10  grammes  of  pure  fluor-spar  yields  17.436 
grammes  of  calcic  sulphate  [76].     Assuming  that  the  atomic  weight 
of  calcium  is  40,  that  of  S0±  96,  and  also  that  the  symbol  of  fluor- 
spar is  CaFv  what  is  the  atomic  weight  of  fluorine  ?  Ans.  19. 

2.  How  much  fluor-spar  and  how  much  sulphuric  acid  must  be 
used  to  generate  sufficient  hydrofluoric  acid  to  neutralize  53  granules 
of  sodic  carbonate  ?  Ttc  •• 

Ans.  39  grammes  of  fluor-spar  and  49  of  sulphuric  acid. 

3.  How  much  liquid  hydrochloric  acid,  Sp.  Gr.  1.1893,  and  how 
much  MnOv  will  yield  one  litre  of  chlorine  gas  ? 

Ans.  3.897  grammes  of  MnO^  and  17.06  grammes  of  hydrochloric 
acid. 

4.  Fifty-nine  grammes  of  metallic  tin  were  dissolved  in  hydro- 
chloric acid  [84],  and  into  this  solution  chlorine  gas  was  passed  until 
all  the  tin  was  converted  into  perchloride.     How  many  litres  of  hy 
drogen  gas  were  evolved  in  the  first  process,  and  how  many  of  chlo- 
rine gas  absorbed  in  the  second  ?  Ans.  11.16  litres  of  each. 

5.  Analyze  reactions   [66  and  79],  and  show  in  what  way  the 
chlorine  gas  acts  as  an  oxidizing  agent. 

6.  Five  grammes  of  liquid  hydrochloric  acid  are  ynixed  with  a 
solution  of  argentic  nitrate,  the  last  being  in  excess.     The  precipi- 
tated argentic  chloride  was  collected,  washed,  dried,  and  weighed. 
The  weight  was  3.206  grammes.     Required  the  per  cent  of  HCl  in 
the  solution.  Ans.  16.31. 

7.  One  volume  of  common  muriatic  acid,  Sp.  Gr.  1.2,  contains 
how  many  volumes  of  HCl  gas  ? 

Ans.  1  c.  m.3,  or  1.200  grammes,  contains  0.489  grammes  of  HCl, 
or  315.8  cTlin3  measured  at  15°  [9]. 

8.  In  order  to  make  one  litre  of  common  muriatic  acid  of  Sp.  Gr. 


212  QUESTIONS  AND  PROBLEMS. 

1.16,  how  much  salt  and  how  much  sulphuric  acid  must  be  used,  and 
how  much  water  must  be  placed  in  the  condenser  ?  [81] 

Ans.  598.9  grammes  of  salt,  1003.  grammes  of  sulphuric  acid,  and 
786.3  grammes  of  water. 

9.  On  what  does  the  economy  of  the  process  [80]  over  [81]  de- 
pend? 

10.  The  reaction  [82]  is  said  to  prove  that  both  hydrogen  and 
chlorine  gas  have  molecules  consisting  of  two  atoms.     On  what  pos- 
tulates does  the  proof  rest  ?     (1 7)  (1 9.) 

11.  One  litre  of  hydrochloric  acid  gas  will  yield  by  [83]  how 
many  litres  of  hydrogen  gas  ?  Ans.  ^  of  a  litre. 

12.  Point  out  the  differences  between  the  reactions  [84,  85,  86, 
and  87],  and  the  relations  on  which  the  differences  depend. 

13.  Show  that  the  compounds  of  chlorine  and  oxygen  may  be  re- 
garded as  compounds  of  chlorine  and  hydroxyl,  less  a  certain  number 
of  molecules  of  water.     What  atomicity  would  it  then  be  necessary 

to  assign  to  chlorine  ? 

vii  vn 

Ans.  For  one  case,  (HO)^Cl  —  3HZ0  =  (£T0)-C7J  0,0,0. 

14.  It  has  been  found  by  very  careful  experiments  that  100  parts 
of  potassic  chlorate  yield  by  [88]  60.85  parts  of  potassic  chloride; 
and  further,  jthat  100  parts  of  potassic  chloride  give  by  precipitation 
192.4  parts  of  argentic   chloride.      Assuming  that  the  symbols  of 
these  compounds  are  those  given  above,  what  must  be  the  atomic 
weights  of  chlorine,  potassium,  and  silver  ?     It  is  also  assumed,  as 
found  by  previous  experiments,  that  the  atomic  weight  of  oxygen  is 
16,  and  that  100  parts  of  silver  combine  with  32.87  of  chlorine. 

Ans.   Cl  =  35.5,  K  =  39.1,  Ag  =  108. 

15.  The  chlorine  gas  evolved  from  1.740  grammes  of  Mn02  is 
passed  into  a  solution  of  potassic  iodide.     How  much  iodine  will  be 
thus  set  free?  Ans.    5.081  grammes. 

16.  Bromine  and  iodine  form  both  with  hydrogen  and  oxygen 
compounds  simHar  to  those  of  chlorine.     Compare  together  the  sev- 
eral compounds  and  point  out  the  resemblances  and  differences  in 
their  properties.     (See  Miller's  Chemistry.) 


123.]  SODIUM.  213 


Division  HI. 

120.  SODIUM.    Na  =  23.  —  Monad.       Combined   with 
chlorine   it  forms  common    salt,   a   substance   which   is   very 
widely  distributed  throughout  nature.     It  also  enters  into  the 
composition  of  a  few  other  minerals  as  an  essential  constituent, 
and  several  of  its  salts  find  important  applications  both  in  the 
arts  and  in  common  life. 

121.  Metallic  Sodium.   Na-Na.  —  Soft,   white  metal  with 
brilliant  lustre,  but  rapidly  tarnishing  in  the  air.     Sp.  Gr.  = 
0.97.     Fuses  at  90°,  and  boils  at  a  red  heat.     When  heated 
in  the  air,  it  burns  with  intensely  yellow  flame.     Decomposes 
water  at  the  lowest  temperatures.     Prepared  by  distilling  in  an 
iron  retort  a  mixture  of  sodic  carbonate  and  charcoal. 


+  2  C  =  STa-SSa  +  3  ®CD.  [89] 

Used  in  the  extraction  of  aluminum,  and  in  the  chemist's  labora- 
tory as  a  powerful  reducing  agent, 

122.  Sodic  Chloride  (Common  Salt).  NaCl  —  White  crys- 
talline salt  (Isometric,  Fig.  7).     Sp.  Gr.  =  2.078.     Melts  at 
red  heat.     Volatilizes  at  white  heat.     Soluble  in  about  three 
times  its  weight  of  water.     Obtained  from  salt-beds  and  by  the 
evaporation  of  saline  waters.    An  essential  article  of  food.     The 
source  of  almost  all  the  sodium  salts.    Used  for  preserving  meat. 

123.  Sodic  Carbonate  (Sal  Soda).  Na.2  C  03.  —  The  crystal- 
lized salt  contains  in  addition  I0ff20,  but  effloresces  in  dry  air. 
White  soluble  salt,  having  an  alkaline  reaction.     Formerly  pre- 
pared by  the  lixiviation  of  the  ashes  of  certain  marine  plants 
called  barilla.      Now  almost  universally  made  from  common 
salt  by  Leblanc's  process.     This  consists,  —  First,  in  treating 
common  salt  with  sulphuric  acid,  which  converts  sodic  chloride 
into  sodic  sulphate. 

2Na  Cfl  +  H,SO,  =  Na2SO,  +  2  SK9L  [90] 

Secondly,  in  melting  on  the  hearth  of  a  reverberatory  furnace 
the  sodic  sulphate  with  chalk  and  fine  coal. 


5Na.2S04  +  20  C  =  5Na2S  +  20  @(S>.  [91] 

,  ICaO  4-  2WD~  T921 


214  SODIUM.  [§  124. 

Thirdly,  by  lixiviating  the  non-volatile  product  of  the  last  re- 
action (called  black-ball)  with  water,  which  dissolves  only  the 
sodic  caroonate.  Used  in  washing,  in  the  manufacture  of  glass 
and  soap,  and  in  the  preparation  of  other  sodium  salts.  Also 
an  important  reagent  in  the  laboratory.  Precipitates  from  so- 
lution of  their  salts  most  of  the  metals,  generally  as  carbonates. 

(CaCL2+Na2C03  +  Aq)=CaCO3+(2NaCl+Aq).  [93] 

When  fused  in  large  excess  with  insoluble  silicates  or  sulphates, 
it  decomposes  them.  Sodic  silicate  or  sulphate  is  formed,  which 
is  soluble  in  water,  and  metallic  carbonates,  soluble  in  acids. 


BaC03  +  Na^SO,  +  (x  —  1)  Na2GOB.  [94] 


124.  Acid  Sodic  Carbonate  (Bicarbonate  of  Soda). 
—  The  crystallized  neutral  carbonate,  when  exposed  to  an  at- 
mosphere of  carbonic  anhydride,  absorbs  the  gas  and  is  converted 
into  this  product  (a  white  powder). 


-f  @©2  =  2ff,Na=C03  +  9ff20.  [95] 

Used,  under  the  name  of  saleratus,  for  raising  bread,  and  in  the 
preparation  of  various  effervescing  powders. 


(ff,Na=C03  +  &K=C4ff406  +  Aq)  = 

Cream  of  Tartar. 


Q  +  JT20  -f  Aq)  +  @©2.  [96] 

Rochelle  Salts. 

125.  Sodic  Hydrate  (Caustic  Soda).  Na-O-H.  —  Amor- 
phous white  solid,  having  very  strong  attraction  for  water,  in 
which  it  dissolves  in  all  proportions,  evolving  considerable  heat. 
Solution  powerfully  alkaline  and  strongly  caustic.  Prepared 
by  adding  milk  of  lime  to  a  solution  of  sodic  carbonate. 

(Na2=C03  +  Ca-(HO),  +  Aq)  = 

Ca=CO3  +  (2Na-HO  +  Aq).   [97] 


To  obtain  the  solid,  the  solution  must  be  decanted  from  the  in- 
soluble chalk  (  Ca  C03)  and  evaporated  to  dryness.  The  solu- 
tion itself  is  a  very  valuable  reagent  in  the  laboratory,  and  a 
crude  solution  (lye)  is  used  in  the  arts  for  making  soap. 


§  130.]  POTASSIUM.  215 

Caustic  soda  will  completely  neutralize  the  strongest  acids.  On 
evaporating  the  neutral  solution,  we  obtain  the  sodic  salt  of  the 
acid  used. 

(NaO-H+  H0-N02  +  Aq)  = 

NaO-N02  +  ff20  +  Aq).   [98] 

(2NaO-ff4-  (HO)2=C202  -f  Ag)  = 

Oxalic  Acid. 

((NaO)fC202  +  2H20  +  Aq).  [99] 

Sodic  salts  of  weak  acids  have  an  alkaline  reaction. 

126.  Oxides  of  Sodium.  —  Sodic  Oxide,  Na^O.    Sodic  Per- 
oxide, Naf(  0-0). 

127.  Sodic  Nitrate  (Chili  Saltpetre  or  Cubic  Nitre).   Na-N0z. 
—  A  natural  product  found  incrusting  the  soil  in  the  desert  of 
Atacama.       Crystallizes  in  rhombohedrons  resembling  cubes. 
Much  used  for  making  nitric  acid. 

128.  POTASSIUM.   K=  39.1.  —  Monad.      An   impor- 
tant constituent  of  felspar  and  mica,  two  very  widely  distrib- 
uted siliceous  minerals.     A  constituent  also  of  all  fertile  soils 
which  are  formed  in  part  by  the  disintegration  of  rocks  con- 
taining these  minerals.     By  the  action  of  atmospheric  agents 
on  the  soil,  soluble  potassium  salts  are  formed  which  are  ab- 
sorbed by  the  growing  plants,  whose  ashes  are  the  chief  source 
of  the  potassium  salts  of  commerce.     But  these  salts  are  now 
also  obtained  from  the  salt-beds  of  Stassfurt  in  Germany. 

129.  Metallic  Potassium.  K-K.  —  Resembles  sodium,  but 
has  a  bluish  tinge  of  color ;  Sp.  Gr.  =  0.865.     Brittle  at  0°. 
Soft  at  15°.    Melts  at  55°.     Sublimes  in  green  vapors  at  a  low 
red  heat.     Burns  when  heated  in  the  air,  and  takes  fire  spon- 
taneously on  water.     Prepared  by  distilling  in  an  iron  retort 
the  intimate  mixture  of  potassic  carbonate  and  charcoal  obtained 
by  charring  crude  tartar.     Reaction  same  as  [89],  substituting 
K  for  Na.     More  powerful  reducing  agent  than  sodium  ;  hence 
obtained  with  greater  difficulty.     More  expensive,  and  less  used 
on  that  account. 

130.  Potassic    Carbonate.    K2COS.  —  White   deliquescent 
salt,  with  strong  alkaline  reaction.     The  crude  salt  (Pot-ashes 
of  commerce)  is  obtained  by  lixiviating  wood-ashes  and  evap- 
orating the  lixivium.   Purified  by  dissolving  in  a  small  quantity 
of  boiling  water,  and  crystallizing  out  the  impurities.     Largely 


216  POTASSIUM.  [§  131. 

consumed  in  the  arts  for  manufacturing  glass  and  soap,  and  for 
preparing  other  compounds  of  potassium. 

131.  Acid  Potassic    Carbonate    (Bicarbonate    of  Potash). 
H,K=CO&.  —  White  crystalline  salt,  prepared  by  passing  C0.2 
through  a  strong  solution  of  the  neutral  carbonate.     Reaction 
like  [95],  substituting  ^Tfor  Na. 

132.  Potassic  Hydrate  (Caustic  Potash).  ff,K=0.  —  White 
amorphous  solid,   prepared   like   caustic  soda  [97],  which  it 
closely  resembles,  but  is  more  deliquescent  and  more  strongly 
alkaline.    Forms  with  fats  "  soft  soaps,"  while  soda  forms  "  hard 
soaps."     Like  caustic  soda,  an  important  reagent  in  the  labor- 
atory.    Precipitates  from  solutions  of  their  salts  most  of  the 
metals,  generally  as  hydrates,  but  sometimes  as  oxides.      In 
some   cases   the   precipitate  is  soluble   in   an   excess  of  the 
reagent. 

(Ca-SO,  +  2K-(HO)  +  Aq)  = 

Ca=(HO)2  +  (KfSOt  +  Aq).  [100] 


-  Aq)  = 
+(R20  +  2K-N03  +  Aq).  [101] 

([A12~\  a,  +  QK-(HO)  +  Aq)  = 

[  AlJi(HO)a  +  (*KCl  +  Aq).  [102] 


[  AIJi(HO)6  +  (SK-HO  +  Aq)  = 

+  SH.,0  +  Aq).  [103] 


Potassic  Aluminate. 


133.  Oxides  of  Potassium.  —  Potassic  Oxide,  K^O.     Po- 
tassic Dioxide,  Kf(O-O).   Potassic  Tetroxide,  Kf(O-O-O-O). 

134.  Potassic  Chloride  (Sylvine).    KCl.  —  Isornorphous  with 
Na  Cl    Found  associated  with  Carnallite  (KGl  .  MyCl2  .  QH.2  0) 
in  the  mines  of  Stassfurt. 

135.  Potassic  Nitrate  (Nitre).  KN03.  —  White  crystalline 
.salt.  Dimorphous.    Usual  form  of  crystals  orthorhombic  prisms, 

but  under  certain  conditions  crystallizes  in  rhombohedra  like 
NaN03  (Hexagonal).  Melts  at  339°  without  decomposition. 
Is  decomposed  at  a  red  heat,  giving  off  a  mixture  of  oxygen  and 
nitrogen  gas.  Deflagrates  on  glowing  coals.  Nitre  is  a  natural 
product,  and  is  chiefly  used  in  the  manufacture  of  gunpowder. 
It  is  also  employed  in  curing  meat,  and  the  fused  salt  (sal  pru- 
nelle)  is  a  useful  medicine 


§  138.]  QUESTIONS  AND  PKOBLEMS.  217 

136.  Characteristic  Reactions.  —  Salts  of  potassium  are  dis- 
tinguished from  those  of  sodium  by  giving  a  precipitate  with  an 
excess  of  tartaric  acid  and  with  acid  platinic  chloride. 

(KCl  +  H,H=C4ff406  +  Aq)  = 

Tartaric  Acid. 

H,K=C4H406  +  (HCl  +  Aq).  [104] 

Acid  Potassic  Tartrate. 

(2KCI  +  PtCflA  +  Aq)  = 

PtCl6K2  +  (2HCH  +  Aq).  [105] 

137.  Lithium,  Rubidium,  and  Ccesium  are  found  in  very 
minute  quantities  in  certain  mineral  waters,  in  lepidolite  mica, 
and  in  a  few  other  rare  minerals.     They  are  always  associated 
with  potassium  and  sodium,  to  which  they  are  closely  allied  in 
all  their  chemical  relations.     They  form  with  sodium  and  po- 
tassium a  series  of  electro-positive  elements  quite  as  well  marked 
as  the  series  of  electro-negative  elements  of  the  previous  group ; 
and,  following  the  same  law,  the  most  electro-positive  elements 
are  the  lowest  in  the  series  and  have  the  highest  atomic  weights. 
Hence,  therefore,  the  chemical  energy  of  the  elements  of  this 
group,  as  manifested  by  the  strength  of  their  affinities  for  ele- 
ments of  the  opposite  class,  like  those  of  the  chlorine  group, 
increases  as  we  descend  in  the  series. 

138.  Characteristic  Reactions.  —  The  compounds  of  each  of 
the  five  "  alkaline  metals  "  impart  a  peculiar  color  to  the  flame 
of  the  Bunsen  lamp.     These  colored  flames,  when  examined 
with  the  spectroscope,  exhibit  characteristic  bands,  by  which 
the  elements  may  be  distinguished,  and  both  rubidium  and  cae- 
sium were  discovered  by  this  means.     (Chapter  XVI.) 


Questions  and  Problems. 

1.  What  is  the  Sp.  Gr.  of  sodium  vapor  V  Ans.  23. 

2.  What  is  the  weight  of  one  litre  of  sodium  vapor  at  1,093°,  but 
under  the  normal  pressure  ?     [9]  and  (1). 

Ans.  Weight  of  hydrogen  gas  under  the  conditions  named  is  1  of 
a  crith.  Hence,  weight  of  sodium  vapor  is  4.6  criths  or 
0.4121  of  a  gramme. 

3.  In  the  preparation  of  sodium  [89]  what  weight  of  metal  ought 
to  be  obtained  from  20  kilos,  of  sodic  carbonate,  and  how  many  litres 

10 


218  QUESTIONS  AND  PROBLEMS. 

of  carbonic  oxide  gas  should  be  formed  for  every  gramme  of  sodium 
obtained  ? 

Ans.  8.680  kilos,  of  sodium  and  1.456  litres  of  carbonic  oxide. 

4.  One  cubic  decimetre  of  rock-salt  contains  how  many  cubic 
decimetres  of  metallic  sodium,  and  how  many  litres  of  chlorine  gas  ? 

Ans.  0.8422  d.  m.3  of  sodium  and  896.5  litres  of  chlorine. 

5.  To  what  extent  is  the  solubility  of  common  salt  influenced  by 
the  temperature  ?     (Fig.  2,  page  108.) 

6.  Given  the  specific  heat  of  common  salt  (0.214),  and  the  atomic 
•weights  of  its  elements  (sodium  and  chlorine),  to  find  its  symbol. 

7.  How  much  carbonate  of  soda  can  be  made  from  500  kilo- 
grammes of  common  salt  ?     How  much  sulphuric  acid  ?     How  much 
coal  and  how  much  chalk  are  required  in  the  process,  according  to 
the  theory? 

Ans.  453  kilos,  of  NaC03,  418.8  kilos,  of  H2SO^  205  kilos,  of  C, 
and  598.2  of  CaCOs. 

8.  What  relation  ought  the  price  of  crystallized  carbonate  of  soda 
to  bear  to  that  of  the  dry  salt,  if  the  intrinsic  value  is  alone  consid- 
ered? Ans.  Price  of  dry  salt  2.7  of  crystallized. 

9.  In  order  to  convert  ten  kilogrammes  of  crystallized  sodic  car- 
bonate into  acid  carbonate,  what  volume  of  C02  will  be  absorbed  ? 

Ans.   780.3  litres. 

10.  What  is  the  difference  between  the  two  sodic  carbonates,  and 
what  is  the  reason  for  the  name  acid  carbonate  ?     (36). 

11.  What  volume  of  C02  can  be  obtained  from  3.72  grammes  of 
acid  sodic  carbonate  ?     [96].  Ans.  1  litre. 

12.  The  symbol  of  sodic  hydrate  may  be  written  Na-O-H,  or 
Na-Ho,  or  (NaO)-H,  and  to  what  three  possible  views  of  its  consti- 
tution do  these  symbols  correspond?     [70]  (235).     Why  should  the 
radicals  HO  or  NaO  be  monads,  and  what  advantage  would  be 
gained  by  writing  the  symbol  in  one  way  or  the  other?     (22)  and 
(28). 

13.  Why  does  calcic  hydrate,  a  comparatively  weak  base,  decom- 
pose sodic  carbonate  ?     (21)  (52). 

14.  A  solution  of  caustic  soda  was  exactly  neutralized  by  0.630 
of  a  gramme  of  crystallized  oxalic  acid  (//02=C202  .  2//20).     What 
weight  of  sodium  does  it  contain  ?  Ans.  0.230  of  a  gramme. 

15.  In  what  different  ways  may  you  write  the  symbol  of  potassic 
nitrate  ?     Illustrate  by  diagrams  like  those  of  (34).     State  what 
rules  must  be  followed  in  grouping  the  atoms.     (22,  28,  34.  and  69.) 

Ans.  K-NOV  KO-NOZ,  or  K-O-NOZ. 


QUESTIONS  AND  PROBLEMS.  219 

16.  What  conclusions  may  be  drawn  in  regard  to  the  distribution 
of  the  soluble  salts  of  sodium  and  potassium  based  on  the  nature  of 
the  plants  from  which  they  are  obtained  ? 

1 7.  On  what  relations  of  solubility  does  the  process  of  purifying 
potassic  carbonate  depend  ? 

18.  If  in  a  chemical  process  potassic  or  sodic  carbonates  may  be 
used  indifferently,  what  relation  ought  their  prices  to  bear  to  each 
other  in  order  that  they  may  be  used  with  equal  profit  ? 

Ans.  138  :  106. 

19.  Analyze  equations  [100,  101,  102,  103],  and  show  that  the 
various  symbols  are  written  in  conformity  to  the  rules  referred  to 
above,  No.  15. 

20.  If  a  saturated  solution  of  nitre  is  made  at  38°,  and  subse- 
quently cooled  to  10°,  what  proportion  of  the  salt  will  crystallize 
out  ?     (Fig.  2.)  Ans.  Two  thirds. 

21.  The  difference  between  the  two  kinds  of  soap  corresponds  to 
what  difference  of  properties  between  sodic  and  potassic  carbonate  ? 

Ans.  The  one  effloresces  and  the  other  deliquesces  in  the  air. 

22.  Draw  diagrams  illustrating  the  constitution  of  the  different 
potassic  oxides.     (34.) 

23.  Why  would  not  the  salts  of  sodium  be  precipitated  by  the 
same  reagents  used  in  [104  and  105]  ?     Apply  the  same  principle  to 
the  interpretation  of  the  other  reactions  of  this  section. 


220  SILVEK.  [§  139. 


Division  IV. 

139.  SILVER.  Ag=  108.  —Monad.      Found   in  small 
quantities  in  nature,  chiefly  in  the  metallic  state,  or  in  com- 
bination with  chlorine,  sulphur,  arsenic,  or  antimony. 

140.  Metallic  Silver.    Ag-Agt  —  Sp.  Gr.  10.474       Fuses 
at  about  1,000°.     The  principal  ores  are 

Native  Silver  Ag-Ag, 

Horn  Silver  AgCl, 

Silver  Glance  Ag.,S, 

Light-red  Silver  Ore  (Proustite)  (AgS)?=As, 

Dark-red  Silver  Ore  (Pyrargyrite)  (AgS)^Sb. 

These  ores  are  found  chiefly  in  mineral  veins  either  by  them- 
selves or  associated  with  ores  of  lead  and  copper,  with  which 
they  are  frequently  smelted,  and  the  silver  subsequently  .sepa- 
rated from  the  regulus  thus  obtained.  Silver  does  not  oxidize 
when  heated  in  contact  with  the  air,  and  for  this  reason  is 
readily  separated  from  lead  in  the  process  of  cupellation. 


xAg2  .  yPb  -f  ^yO~-  0  ==  xAg-Ag  -f  yPb  0.      [106] 

The  cupel  furnace  is  so  arranged  that  the  melted  litharge  (PbO) 
runs  off  as  fast  as  formed,  and  leaves  the  silver  pure.  Melted 
silver  can  dissolve  about  twenty-two  times  its  volume  of  oxy- 
gen gas  ;  but  the  gas  is  given  off,  in  great  measure,  when  the 
metal  solidifies. 

141.  Argentic  Nitrate.  AgN03.  —  The  most  important  sol- 
uble salt  of  silver.  Obtained  by  dissolving  silver  in  dilute  ni- 
tric acid. 

3Ag-Ag  +  (SffNO,  +  Aq)  = 

(6AgN03  +  4ff20  +  Aq)  +  23SST®.  [107] 

White  crystalline  solid  which  melts  at  219°.  Fused  salt  is 
called  lunar  caustic,  and  is  much  used  in  surgery  as  a  cautery. 
Argentic  nitrate,  although  not  changed  by  the  light  when  pure, 
is  readily  decomposed  when  in  contact  with  organic  matter,  and 
the  black  stain  of  metallic  silver  thus  formed  cannot  be  removed 
by  washing.  Hence  its  application  for  making  hair  dyes  and 


§  143.}-  SILVER.  221 

indelible  ink.     It  is  also  used  in  large  quantities  in  the  art  of 
photography. 

142.  Argentic  Chloride.  AgCL  —  White  crystalline  solid 
(Fig.  7).  Melts  at  about  260°,  and  on  cooling  forms  a  horny 
sectile  mass,  whence  the  mineralogical  name,  horn  silver.  Pre- 
pared by  adding  to  a  solution  of  argentic  nitrate  any  soluble 
chloride. 


(AffN08  +  NaCl  +  Aq)  =  AgCl  +  (NaNO,  +  Aq).  [108] 

We  thus  obtain  a  white  curdy  precipitate,  which  is  insoluble  in 
water  and  acids,  but  soluble  in  ammonia,  in  potassic  cyanide, 
and  in  sodic  hyposulphite.  Owing  to  a  partial  reduction,  the 
white  powder  blackens  in  the  light,  especially  in  the  presence 
of  organic  matter  and  an  excess  of  argentic  nitrate.  On  this 
property  is  based  the  ordinary  process  of  photographic  printing. 
In  contact  with  dilute  acids,  argentic  chloride  is  very  readily 
reduced  by  metallic  zinc. 

2Ag  Gl  -f  Zn,  =  Zn  C12  +  Ag2.  [109] 

It  may  also  be  reduced  by  hydrogen  or  hydrocarbon  gas  passed 
over  the  chloride  in  a  heated  tube. 


[110] 

In  the  process  of  electro-plating,  argentic  chloride,  dissolved  in 
an  aqueous  solution  of  potassic  cyanide,  is  decomposed  by  the 
electric  current.  (91). 

143.  Argentic  Bromide^  AgBr,  and  Argentic  Iodide,  Agl, 
resemble  argentic  chloride,  and  are  formed  in  a  similar  way. 
The  last,  however,  has  a  yellow  color,  and  is  insoluble  in  am- 
monia. In  presence  of  an  excess  of  argentic  nitrate,  and  after 
exposure  to  light,  they  are  at  once  reduced  to  the  metallic  state 
by  solution  of  ferrous  sulphate.  Before  exposure  the  reduction 
takes  place  very  slowly,  and  on  this  reaction  is  based  the  art 
of  photography.  The  steps  of  the  process  are  :  1.  Spreading 
over  a  glass  plate  a  film  of  collodion,  holding  in  solution  a  mix- 
ture of  metallic  bromides  and  iodides  ;  2.  Immersing  the  coated 
plate  in  a  solution  of  argentic  nitrate  until  a  mixture  of  argen- 
tic bromide  and  iodide  is  formed  in  the  film  ;  3.  Exposing  the 
plate  to  light  in  the  camera,  where  the  image  formed  by  a  lens 
falls  upon  it  ;  4.  Developing  the  latent  image  by  a  solution  of 


222  THALLIUM.  —  GOLD.  [§  144 

ferrous  sulphate ;   5.  Dissolving  out  the  undecomposed  silver 
salt  by  a  solution  of  sodic  hyposulphite. 

144.  Argentic    Oxide.  Ag20.      Argentic   Peroxide.  Ag202. 
—  The  first  is  very  slightly  soluble  in  water,  and  the  solution 
has  an  alkaline  reaction. 

145.  Characteristic  Tests.  —  Most  silver  compounds  may  be 
reduced  to  pure  silver  before  the  blow-pipe;   and  whenever 
they  are  brought  into  solution  the  silver  can  be  recognized  and 
the  amount  very  accurately  determined  by  the  reaction  just 
given.     [108].     Silver  is  remarkable  for  forming  anhydrous 
salts ;  and  whenever  we  wish  to  determine  the  molecular  weight 
of  an  acid,  it  is  generally  best  to  analyze  its  silver  salt.      (68). 


Division  V. 

146.  THALLIUM.  Tl  =  204.  —  Usual  quantivalence 
one,  but  atomicity  probably  three.  A  very  rare  element,  found 
in  some  varieties  of  pyrites.  Its  oxide,  T120,  is  soluble  in 
water,  and  absorbs  carbonic  anhydride  from  the  air.  v  Its  vapor 
imparts  a  green  color  to  the  flame  of  a  Bunsen  lamp,  and  shows 
a  single  green  band  in  the  spectroscope. 


Division  VT* 

147.  GOLD.  Au  =  197.  —  Triad.  Probable  molecular 
symbol  of  metal,  Au=Au.  Almost  always  found  in  the  native 
state,  or  only  slightly  alloyed  with  other  metals.  The  only 
well-defined  native  compounds  are  those  with  Tellurium. 
Very  sparingly  but  very  widely  disseminated  through  many  of 
the  crystalline  rocks  and  in  the  alluvium  resulting  from  their 
disintegration.  In  the  gold-bearing  rocks  the  metal  is  frequently 
found  accumulated  to  a  greater  or  less  extent  in  veins  of  quartz 
(auriferous  quartz).  It  is  also  constantly  associated  in  minute 
quantities  with  other  metallic  ores,  especially  with  those  of  sil- 
ver, and  in  some  localities  the  veins  of  iron  and  copper  pyrites 
yield  large  amounts  of  the  precious  metal.  It  is  extracted 
either  by  simple  washing  or  by  bringing  the  finely  pulverized 
ore  in  contact  with  metallic  mercury,  which  has  a  great  affinity 
for  gold  and  picks  out  the  minute  particles  from  the  mass  of 


§  147.]  •  GOLD.  223 

refuse.  The  process  is  very  simple,  and  the  cost  of  the  product 
depends,  to  a  great  extent,  on  the  very  large  amount  of  material 
which  must  be  handled;  for  gold  ores  do  not  on  the  average 
contain  but  a  few  ounces  of  metal  to  the  ton.  From  the  re- 
sulting amalgam  the  mercury  is  recovered  by  distillation,  and 
the  residual  metal  may  then  be  melted  and  cast  into  bars.  The 
gold  thus  obtained,  however,  is  more  or  less  alloyed,  chiefly 
with  silver,  and  is  refined  before  being  used  for  coinage.  This 
is  best  accomplished  by  dissolving  the  metal  in  aqua-regia, 
evaporating  to  dryness  to  remove  the  excess  of  nitric  acid,  dis- 
solving in  a  large  volume  of  water,  and  precipitating  the  gold 
with  ferrous  sulphate.  Lastly,  the  precipitate  is  collected  and 
melted  under  borax.  If  the  proportion  of  alloy  is  very  large, 
it  is  best  removed  by  boiling  the  metal  with  nitric  or  sulphuric 
acid.  When  nitric  acid  is  used  for  parting  gold  from  silver, 
the  separation  is  not  complete  when  the  amount  of  gold  is 
more  than  one  fourth  of  the  weight  of  the  alloy ;  and  since  in 
most  cases  the  alloy  must  be  first  reduced  to  this  proportion, 
the  process  is  called  quartation.  When  sulphuric  acid  is  used, 
the  amount  -of  gold  must  not  exceed  one  fifth. 

Gold  has  been  called  the  king  of  metals  ;  for  it  not  only  pos- 
sesses the  qualities  distinguishing  a  metal  in  their  highest  per- 
fection, but  also,  under  all  ordinary  conditions,  preserves  its 
brilliant  lustre  unimpaired.  With  the  exception  of  platinum, 
iridium,  and  osmium,  gold  is  the  densest  solid  known ;  Sp.  Gr. 
19.34.  It  may  be  drawn  into  wire  of  such  fineness  that  three 
kilometres  only  weigh  a  single  gramme,  and  may  be  beaten 
into  leaves  not  more  than  one  ten-thousandth  of  a  millimetre 
thick.  Gold  has  a  familiar  yellow  color,  but  thin  leaves  trans- 
mit a  green  light.  It  has  been  found  that  an  exceedingly  thin 
film  of  gold  attached  to  the  surface  of  a  glass  plate,  and  heated 
to  a  temperature  not  exceeding  315°,  loses  its  metallic  lustre 
and  appears  ruby-red  by  transmitted  light ;  and  finely  divided 
gold,  when  suspended  in  water  or  melted  into  glass,  imparts  to 
the  medium  the  same  beautiful  color.  Gold  is  nearly  as  soft  as 
lead,  and  pieces  of  pure  gold  may  be  welded  together  without 
heat  by  pressure  or  concussion,  as  in  dentistry.  In  order  to 
increase  its  hardness  it  is  alloyed  with  copper.  The  standard 
gold  of  both  the  United  States  and  the  French  coinage  contains 
one  tenth  copper,  that  of  the  English  one  twelfth  of  the  same 


224  GOLD.  [§  147. 

alloy.  Gold  melts  at  about  1,100°.  It  is  only  slightly  volatile 
at  the  highest  furnace  heat  ;  but  before  the  compound  blow-pipe 
it  is  dispersed  in  purple  vapor.  It  is  an  excellent  conductor  of 
heat  and  electricity,  but  is  inferior  in  this  respect  both  to  silver 
and  copper. 

Gold  is  not  dissolved  by  any  of  the  common  acids,  and  is  not 
attacked  by  the  fused  caustic  alkalies.  It  enters,  however,  into 
direct  union  both  with  chlorine  and  bromine,  and  is  readily  dis- 
solved by  any  liquid  mixture  which  liberates  chlorine.  The  usual 
solvent  is  a  mixture  of  four  parts  of  hydrochloric  acid  with  one 
of  nitric  acid,  called,  on  account  of  its  power  of  dissolving  gold, 
aqua-regia. 


Au*Au  +  (2ffN03  +  QHCl  +  Aq)  = 

(2AuCl3-\-  4ff20  +  Aq)  +  2S5T®.  [111] 


When  gold  is  dissolved  in  aqua-regia,  if  hydrochloric  acid  is 
used  in  excess,  the  solution,  evaporated  at  a  gentle  heat,  yields 
yellow  needle-shaped  crystals,  which  appear  to  be  a  molecular 
compound  of  AuCl3  with  HCL  If,  however,  the  evaporation 
is  pushed  still  further,  but  at  a  temperature  not  exceeding  120°, 
a  red  crystalline  mass  is  obtained,  which  is  essentially  Auric 
Chloride,  An  Cl&  although  it  is  difficult  to  expel  the  last  traces 
of  HGl  without  still  further  decomposing  the  salt.  If  this  pro- 
duct is  heated  above  160°  it  loses  two  atoms  of  chlorine,  and 
there  is  left  a  pale-yellow,  sparingly  soluble  powder,  which  is 
Aurous  Chloride,  Au  Cl,  and  at  200°  this  last  is  also  decom- 
posed and  reduced  to  metallic  gold.  Auric  chloride  is  deli- 
quescent, and  yields  an  orange-colored  solution  easily  distin- 
guished from  the  solution  of  Au  C13  .  HCl,  which  is  yellow.  It 
also  forms  yellow  crystalline  salts  with  the  alkaline  chlorides, 
similar  in  constitution  to  the  compounds  with  HCL  Their  for- 
mulas are  Au  Cls  .  KCl  .5ff20,  and  Au  C18  .NaCl.^ff,  0.  In 
like  manner  it  unites  with  ammonic  chloride  and  with  the  chlo- 
rides of  most  of  the  organic  bases,  forming  crystallizable  salts, 
which  are  often  employed  to  determine  the  molecular  weight  of 
these  alkaloids.  Auric  chloride  is  a  very  unstable  compound, 
and  is  readily  reduced  to  the  metallic  state.  Solutions  of  fer- 
rous sulphate,  of  antimonious  chloride,  of  oxalic  acid,  and  of 
sulphurous  acid,  all  precipitate  the  gold  in  a  finely-divided 
state.  Phosphorous  and  hypophosphorous  acid  and  solutions 


§  147.]  GOLD.  225 

of  their  salts  produce  the  same  effect,  as  do  also  phosphorus  it- 
self and  many  of  the  metals.  The  brown  gold  powder  thus  ob- 
tained is  much  used  for  gilding  porcelain.  A  solution  of  stan- 
nous  chloride  mixed  with  stannic  chloride  produces  in  neutral 
solution  of  auric  chloride  a  beautiful  purple  precipitate  called 
Purple  of  Cassius,  which  is  much  used  for  coloring  glass  and 
porcelain.  The  compound  contains  both  gold  and  tin  combined 
with  oxygen,  but  its  chemical  constitution  is  still  in  question. 
Metallic  tin  gives  a  similar  precipitate.  There  appear  to  be 
two  iodides  of  gold,  Auland  Aul&  but  only  one  bromide,  AuBr& 
has  been  described.  There  are  also  two  oxides,  Au203  and 
Au2  0.  The  first  acts  as  an  acid,  the  second  as  a  very  feeble 
basic  anhydride.  The  following  reactions  illustrate  the  forma- 
tion and  relations  of  these  compounds. 


(AuCl3  +  GK- 

(KfOfAu  +  3KCI  -\-3ff20  +  Aq).  [112] 

u  +  3ff-0-O2ff30  +  Aq)  = 

(%K-0-C2H30  -}-  Aq).  [113] 

u  =  Au203  +  3ff20.  [114] 

To  obtain  these  reactions,  the  solution  o?AuCl3  should  be  boiled 
after  the  addition  of  K-0-ffa.ud.  then  acidified  with  acetic  acid. 
The  precipitate  thus  obtained  has,  when  dried,  the  composition 
of  Au203.  The  compound  Au20  is  obtained  as  an  insoluble  vi- 
olet powder  by  digesting  Au  Cl  with  a  solution  of  caustic  alkali. 

(2AuCl  +  2Na-0-H-\-  Aq)  = 

Au20+(2NaCl+ff20  +  Aq).  [115] 

It  does  not  enter  into  direct  combination  with  acids,  but  there 
is  an  hyposulphite  of  gold  and  sodium  which  plays  an  impor- 
tant part  in  photography,  and  appears  to  have  the  formula 
Au,Na=0.2=(S-0-S).  Singularly,  however,  gold  is  not  precipi- 
tated from  the  solution  of  this  salt  by  the  ordinary  reagents. 
There  are  two  sulphides  of  gold,  Au^  and  Au2S.  The  first 
is  precipitated  by  ff2S  from  a  cold  solution  and  the  last  from  a 
boiling  solution  of  AuCl3  by  the  same  reagent.  They  both 
dissolve  in  alkaline  sulphides  and  form  sulphur  salts.  Thus 


u  +  Aq)  +  3ff2S.  [116] 
10*  o 


226  QUESTIONS  AND  PEOBLEMS.  [§148. 

148.  Characteristic  Reactions.  —  With  the  exception  just 
noticed,  gold,  when  in  solution,  can  be  distinguished  by  the  fact 
that  it  is  precipitated  by  ferrous  sulphate,  provided  the  solution, 
though  -acid,  does  not  contain  an  excess  of  nitric  acid. 


(2AuCls  +  QFe=02=S0.2  +  Ag)  = 

[117] 


The  formation  of  purple  of  Cassius,  and  the  easy  reduction  of 
all  the  compounds  to  the  metallic  state  by  simple  ignition,  are 
other  indications  by  which  the  presence  of  gold  may  be  readily 
recognized.  The  reduced  gold,  even  when  in  fine  powder,  ac- 
quires its  peculiar  lustre  if  rubbed  against  a  hard  surface,  as  in 
the  process  of  burnishing.  Besides  the  important  uses  of  gold 
for  coinage  and  for  articles  of  ornament  or  luxury,  the  metal  is 
peculiarly  well  adapted,  both  by  its  softness  and  its  power  of 
resisting  corrosive  agents,  for  its  applications  in  dentistry.  It 
is  also  largely  employed  in  the  various  methods  of  gilding, 
which  consists  either  in  directly  applying  thin  gold-leaf  to  the 
surface  to  be  covered,  or,  when  the  surface  is  metallic,  by  de- 
positing upon  it  a  thin  film  of  gold  with  the  aid  of  galvanism 
or  by  the  simple  action  of  chemical  affinity. 


Questions  and  Problems. 

1.    Given  the  percentage  composition  of  Proustite.    Silver,  65.45; 
Sulphur,  19.39;  Arsenic,  15.16.     Required  the  symbol. 

Ans.  Ag3S3As. 

2    How  much  greater  is  the  per  cent  of  silver  in  Proustite  than 
in  Pyrargyrite  ?  Ans.  5.68  per  cent. 

3.  Draw  diagrams  illustrating  the  molecular  constitution  of  the 
different  silver  ores. 

4.  Analyze  reaction  [107],  and  point  out  the  difference  between 
it  and  the  class  of  reactions  of  which  [64]  is  the  type. 

5.  If  a  given  mass  of  argentiferous  lead  contains  three  fourths  of 
one  per  cent  of  silver,  how  many  kilogrammes  of  litharge  will  be 
made  in  the  process  of  cupellation  to  each  kilogramme  of  silver  ex- 
tracted, and  how  many  cubic  metres  of  oxygen  gas  will  be  absorbed 
by  the  process  ? 

Ans.  142.5  kilos,  of  litharge,  and  7.134  in?  of  oxygen. 


QUESTIONS  AND  PROBLEMS.  227 

6.  One  gramme  of  silver  treated  as  indicated  by  [107]  and  [108] 
yielded   1.328  grammes  of  argentic  chloride.     What  is  the  atomic 
weight  of  silver  ?     The  atomic  weight  of  chlorine  is  assumed  to  be 
known,  35.5,  and  also  the  specific  heat  of  argentic  chloride,  0.091. 

Ans.  108. 

7.  One  gramme  of  argentic  chloride  reduced  by  hydrogen  [110] 
yielded  0.7526  of  a  gramme  of  silver.     What  is  the  atomic  weight 
of  silver  ?     The  same  values  are  assumed  as  in  the  last  problem. 

Ans.  108.- 

8.  One  gramme  of  argentic  oxalate  yields  when  heated  0.7105  of 
a  gramme  of  silver.     We  have  reason  to  believe  that  oxalic  acid  is 
bibasic.     What  is  its  molecular  weight  ?     (68).  Ans.  90. 

9.  Write  the  reactions  of  sulphurous  acid  and  of  oxalic  acid  on 
solution  of  auric  chloride,  assuming  that  sulphuric  acid  in  one  case, 
and  COZ  in  the  other,  are  a  part  of  the  products. 

10.  What  evidence  do  you  find  of  the  quantivalence  of  gold  in  the 
above  sections  ? 

11.  Does  gold  act  as  an  acid  or  a  basic  radical  ? 

12.  What  is  the  chief  chemical  characteristic  of  gold? 

13.  There  has  been  a  question  about  the  cause  of  the  color  which 
purple  of  Cassius  imparts  to  glass  and  porcelain  glaze.     Do  the  facts 
stated  aboye  explain  this  phenomenon  ? 


228  BORON.  [§  149. 


Division  VII. 

149.  BORON.  B  =  11.  —  Triad.  Very  sparingly  distrib- 
uted. Always  found  in  combination  with  oxygen.  In  boric  acid 
and  in  various  borates,  including  the  minerals  Datholite  and 
Danburite,  boron  is  the  electro-negative  element,  while  in  Axi- 
nite  and  Tourmaline,  and  in  many  artificial  salts,  it  acts  the  part 
of  a  basic  radical.  The  elementary  substance  (B=Bt)  may  be 
obtained  both  in  an  amorphous  and  a  crystalline  form.  The 
first  is  obtained  by  decomposing  boric  anhydride  with  sodium. 

B203  +  3Na-Na  =  3Na20  +  B~=B.  [118] 

It  is  an  infusible  dark-brown  powder,  which  soils  the  fingers 
and  dissolves  slightly  in  water.  At  about  300°  it  takes  fire  in 
the  air  and  burns  into  B203,  and  it  is  also  oxidized  when  heated 
with  sulphuric  acid  or  with  the  alkaline  nitrates,  sulphates,  car- 
bonates, or  hydrates.  It  decomposes  nitric  acid  even  when 
slightly  concentrated  and  cold. 

[119] 
[120] 

Boron  is  one  of  the  very  few  elements  which  unite  directly  with 
nitrogen. 

B=-B  -f  AW—  2B~=N.  [121] 

If  amorphous  boron  is  heated  intensely  in  a  closed  crucible,  it 
becomes  much  denser,  and  is  then  less  easily  oxidized.  It  dis- 
solves in  melted  aluminum,  and  when  the  molten  metal  sets,  the 
boron  crystallizes  in  quadratic  octohedrons  (75)  more  or  less 
highly  modified.  These  crystals  are  nearly  as  hard  as  the  dia- 
mond, have  an  adamantine  lustre,  and  Sp.  Gr.  =  2.68.  They 
may  also  be  obtained  directly  from  boric  anhydride,  which  is 
decomposed  by  aluminum. 

[^2]  +  B203  =  [^]  03  +  B-=B.  [122] 

The  crystals  thus  prepared  are  sometimes  nearly  colorless, 
but  more  frequently  they  have  a  yellow  or  red  color,  and  some- 
times the  color  is  so  deep  that  they  appear  black.  They  are 


§  150.]  BORON. 

probably  never  wholly  pure,  and  it  is  worthy  of  remark  that 
they  sometimes,  if  not  always,  contain  a  considerable  quantity 
of  carbon.  They  resist  the  action  of  all  acids,  and  even  of  fused 
nitre,  but  are  oxidized  when  fused  with  acid  potassic  sulphate. 
It  appears,  from  recent  investigations,  that  the  so-called  graphi- 
toidal  boron,  which  is  formed  with  the  crystals  just  mentioned, 
is  a  compound  of  aluminum  and  boron. 

150.  Boric  Acid.  HfO^B.  —  A  product  of  volcanic  action. 
Found  in  some  natural  waters,  and  has  been  detected  in  the 
waters  of  the  ocean.  It  is  collected  in  large  quantities,  but  in 
an  impure  condition,  from  the  hot  vapors  of  the  "fumerolles  " 
in  the  Maremma  of  Tuscany.  The  pure  acid  is  best  prepared 
from  borax  by  the  reaction 

+  2ffCl  +  5ff20  +  Ag)  = 

(2NaCl+Aq).  [123] 


The  hydrochloric  acid  should  be  mixed  with  a  hot  saturated  so- 
lution of  borax,  which  as  it  cools  deposits  boric  acid  in  white 
nacreous  crystalline  scales.  Boric  acid  is  sparingly  soluble 
in  cold  water,  but  dissolves  in  three  times  its  weight  of  boiling 
water.  It  is  also  soluble  in  alcohol,  and  imparts  to  the  flame 
of  burning  alcohol  a  peculiar  green  tint,  which  exhibits  in  the 
spectroscope  five  well-marked  green  bands.  The  solution  both 
in  water  and  in  alcohol  cannot  be  evaporated  without  loss,  as 
the  vapor  always  takes  with  it  an  appreciable  amount  of  the 
acid.  The  solution  evaporated  on  turmeric  paper  changes  the 
color  to  brown,  like  an  alkali,  but  it  affects  litmus  paper  like 
other  weak  acids.  At  the  temperature  of  100°  it  loses  one 
atom  of  water. 

HfOfB  =  H-O-BO  +  2T20.  [124] 

The  compound  H^OfB  is  called  orthoboric  acid.  The  pro- 
duct H-O-BO  is  frequently  described  as  the  first  anhydride  of 
this  acid,  and  is  called  metaboric  acid.  If  this  is  heated  to  a 
still  higher  temperature  two  molecules  unite,  while  at  the  same 
time  they  lose  another  atom  of  water,  forming  the  second  and 
last  anhydride,  boric  anhydride. 

ZH-O-BO  =  B.203  +  H20.  [125] 

At  a  red  heat  B2  03  fuses  to  a  viscid  glass,  which  remains  clear 


230  BORON.  [§  151. 

as  it  cools,  but  soon  becomes  opaque  and  crumbles  if  exposed 
to  the  air.  It  also  forms  fusible  compounds  with  the  metallic 
oxides.  Hence  the  use  of  boric  acid  and  the  borates  as  fluxes. 
151.  Borates.  —  It  is  evident  from  the  principles  of  (38) 
that,  besides  orthoboric  acid,  many  others  are  theoretically  pos- 
sible. Thus:  — 

Boric  Acid  HOB 


Diboric  Acid  L 

Triboric  Acid  H6l 05^(B- 0-B- 0-B), 

Tetraboric  Acid  ff6W^(B-0-B-0-B-0-B), 

Polyboric  Acid  Hn  +2  On  +  2(Bn On ^ 

These  may  be  regarded  as  formed  by  the  coalescing  of  sev- 
eral molecules  of  orthoboric  acid,  and  the  elimination  from  this 
condensed  molecule  of  a  sufficient  number  of  molecules  of  water 
to  set  free  the  number  of  oxygen  atoms  required  to  cement  to- 
gether the  atoms  of  boron  in  the  resulting  radical.  By  .elimi- 
nating additional  molecules  of  water,  we  may  obtain  from  either 
of  the  above  acids  a  series  of  anhydrides  (distinguished  as  the 
first,  second,  &c.,  anhydrides),  and  the  number  of  possible  an- 
hydrides in  any  case  is  equal  to  the  number  of  pairs  of  hydro- 
gen atoms  which  the  acid  contains.  It  must  be  understood  that 
all  these  possible  forms  are  not  real  compounds.  Indeed,  only 
the  three  already  mentioned  have  been  actually  prepared ;  but 
there  are  several  borates  whose  constitution  is  best  explained 
when  we  regard  them  as  salts  of  acids  derived  from  orthoboric 
acid  in  the  way  just  indicated.  The  most  important  of  these 
is  common  borax,  which  may  be  regarded  as  the  sodium  salt  of 
the  second  anhydride. of  tetraboric  acid. 

152.  Borax,  Na2=02=(B=02=B-0~B=02=B)  .I0ff20,  was  orig- 
inally brought  from  a  salt  lake  in  Thibet,  and  was  called  Tincal. 
It  also  occurs  in  large  crystals  in  the  mud  of  Borax  Lake,  in 
California,  and  it  has  been  found  in  solution  in  many  mineral 
springs,  and  even  in  minute  quantities  in  the  ocean.  Is  man- 
ufactured in  large  quantities  from  the  crude  boric  acid  of  the 
Tuscan  lagoons.  White  crystalline  salt,  which  when  heated 
gives  up  its  water  of  crystallization.  At  a  red  heat  melts  to  a 
transparent  glass,  which  has  the  property  of  dissolving  almost 


§  153.]  BORON.  231 

all  the  metallic  oxides.  Many  of  them  impart  to  the  glass 
characteristic  colors  ;  and  these  reactions,  which  are  readily  ob- 
tained with  a  small  bead  of  borax  supported  by  a  loop  of  plat- 
inum wire,  are  useful  blow-pipe  tests.  It  is  also  used  for  solder- 
ing metals,  for  making  enamels,  for  fixing  colors  on  porcelain, 
and  as  a  flux  in  various  metallurgical  processes.  The  ordinary 
crystals  contain  as  above  IOR20,  and  belong  to  the  monoclinic 
system  ;  but  the  salt  can  be  crystallized  with  only  5If20  in  oc- 
tahedrons belonging  to  the  isometric  system. 

153.  Boric  Chloride,  BC13,  can  be  obtained  by  passing  chlo- 
rine gas  over  an  intimate  mixture  of  B2  03  and  carbon,  heated 
to  a  red  heat  in  a  porcelain  retort. 


B.203  -f  3G  +  3Cl-Cl=  3OO  +  2BO13.      [126] 


It  is  a  very  volatile  liquid  (Sp.  Gr.  1.35  at  7°),  boiling  at  17°, 
and  yielding  a  dense  vapor  whose  Sp.  Gr.,  as  found  by  experi- 
ment, is  56.85  ;  chiefly  interesting  as  establishing  the  quanti- 
valence  of  boron.  It  is  at  once  decomposed  by  water. 


BCl,  +  3ff20  =  ff3-=03-=B  +  3HCI.          [127] 

154.  Boric  Bromide,  BBr&  prepared  like  the  chloride,  is  a 
volatile  liquid  (Sp.  Gr.  2.69),  boiling  at  90°,  and  giving  a  vapor 
whose  Sp.  Gr.  has  been  found  by  experiment  equal  to  126.8. 
Decomposed  by  water  like  the  chloride. 

155.  Boric  Fluoride,  BF&  is  best  prepared   by   intensely 
heating  a  mixture  of  B203  and  fluor-spar. 


2B,  03  +  3  GaF2  =  Ca3W6W2  +  2BF3.        [128] 

A  colorless  gas,  whose  Sp.  Gr.  has  been  found  by  experiment 
equal  to  34.2.  This  gas  is  eagerly  absorbed  by  water,  which 
dissolves  seven  hundred  times  its  volume  and  forms  a  corrosive 
acid  liquid  called  borofluoric  acid,  whose  constitution  is  not  well 
understood.  If  its  composition  is  that  usually  assigned  to  it,  its 
formation  will  be  expressed  by  the  reaction 


2BF3  +  3ff20  =  B203  .  GffF.  [129] 

The  same  compound  may  be  also  prepared  by  dissolving  B.2  03 
in  HF  -|-  Aq,  and  then  concentrating  the  solution. 

If  borofluoric  acid  is  largely  diluted  with  water,  one  fourth 


232  QUESTIONS  AND  PROBLEMS.  [§  156.' 

of  the  boron  separates  in  the  form  of  boric  acid,  and  there  is 
left  in  solution  what  has  been  called  hydrofluoboric  acid. 


Aq).  [130] 

Hydrofluoboric  acid  forms  salts  with  basic  radicals,  and  the 
compound  with  potassium  may  be  formed  by  the  action  of  boric 
acid  on  a  dilute  solution  of  potassic  fluoride. 


(SKF  +  2fff 

2(KF.  £F3)  +  (6K-0-H+  Aq).  [131] 

156.  Characteristic  Reactions.  —  The  peculiar  green  color 
which  boric  acid  imparts  to  an  alcohol  or  blow-pipe  flame  is  the 
best  indication  of  its  presence,  and  this  test  is  made  still  more 
decisive  by  analyzing  the  colored  light  with  the  spectroscope. 
The  acid,  however,  must  first  be  set  free  before  the  reaction 
can  be  obtained.  In  many  of  its  relations  boron  resembles 
carbon. 


Questions  and  Problems. 

1.  Write  the  reaction  of  sulphuric  acid  on  solution  of  borax. 

2.  What  test  can  be  applied  to  determine  when  an  excess  of  sul- 
phuric acid  has  been  added  ? 

3.  Define  an  ortho  acid,  regarding  orthoboric  acid  as  a  type  of 
the  class. 

4.  Make  a  table  showing  the  relations  of  the  various  possible  de- 
rivatives of  boric  acid. 

5.  The  empirical  symbol  of  boracite  is  Mg3Ol5By     What  is  its  ra- 
tional symbol,  and  what  is  its  relation  to  the  ortho-borates  ? 

6.  Boric  sulphide,  BtS#  may  be  prepared  by  passing  over  a  mix- 
ture of  carbon  and  boric  anhydride  the  vapor  of  carbonic  sulphide, 
CSV     The  products  are  2B2SS  and  SCO.     Write  the  reaction. 

7.  Boric  sulphide  is  readily  decomposed  by  water,  giving  boric 
acid  and  sulphuretted  hydrogen.     Write  the  reaction. 

8.  In  reaction  [126]  what  double  affinities  are  called  into  play? 

9.  In  what  respect  do  you  find  reaction  [131]  remarkable  ? 

10.  What  evidence  do  you  find  of  the  prevailing  quanti valence  of 
boron  ?     Are  there  any  facts  which  would  indicate  that  boron  is  a 
pentad  ? 


§  158.]  NITROGEN.  233 


Division  Vlll. 

157.  NITROGEN.   N=  14.  —  Pentad,  but  as  frequently 
trivalent  or  univalent.     Chief  constituent  of  the  atmosphere  ; 
but  to  this  and  the  materials  of  organized  beings  it  is  almost 
exclusively  confined.     It  is  the  characteristic  ingredient  of  ani- 
mal tissues,  which  are  composed  mainly  of  the  four  elements 
carbon,  hydrogen,  oxygen,  and  nitrogen.     Vegetable  tissues,  on 
the  other  hand,  consist  chiefly  of  only  the  first  three  of  these 
elements  ;  but  nitrogen  is  never  entirely  absent  from  plants,  and 
is  an  essential  ingredient  of  many  important  vegetable  products, 
as,  for  example,  of  the  albuminoid  compounds  and  of  the  vege- 
table alkaloids.     Nitrogen  is  marked  by  weak  affinities,  and 
hence  its  compounds  are  usually  unstable,  as  is  illustrated  by 
the  well-known  tendency  of  animal  substance  to  decay. 

158.  Nitrogen  Gas,  N=N,  constitutes  four  fifths  of  the  vol- 
ume of  the  atmosphere,  and  can  be  obtained  in  a  pure  condi- 
tion, —  First,  by  slowly  or  rapidly  burning  phosphorus  in  a  con- 
fined volume  of  air.      Secondly,  by  passing  air  over  ignited 
copper-turnings,  which  combine  with  the  oxygen.     Thirdly,  by 
passing  chlorine  gas  through  a  solution  of  ammonia,  — 

(8ffsN+  Aq)  +  3  Cl-  Cl  =  (GfftNCl  +  Ag)  +  NiN.  [132] 

Fourthly,  by  heating  ammonic  nitrite  or  a  mixture  of  potassic 
nitrite  and  ammonic  chloride,  — 


(HJf)  -0-NO  =  2ff,  0  +  mN.  [133] 

K-O-NO  +  (HJST)  Cl  =  KGl  +  2R20  +  mff.  [134] 

Nitrogen  gas  has  never  been  condensed  to  a  liquid  condition. 
According  to  Regnault,  one  litre  of  nitrogen  gas,  under  standard 
conditions,  weighs  1.256167  grammes.  It  is  remarkable  for  its 
inertness,  and  one  of  its  chief  offices  in  the  atmosphere  is  to 
moderate  the  action  of  its  violent  associate.  The  only  element- 
ary substances  with  which  it  directly  combines  are  boron  and 
titanium.  Nevertheless,  nitrogen  has  a  great  capacity  for  com- 
bination, and  is  distinguished  by  the  large  number  and  varied 


234                                     NITROGEN.  [§  159. 

nature  of  Its  compounds ;  but  these  can  only  be  formed  by  in- 
direct methods. 

Oxides  of  Nitrogen. 

Nitrous  Oxide  N20, 

Nitric  Oxide                NO,  m 

Nitrous  Anhydride    N20&         Nitrous  Acid  H-O-NO, 

Nitric  Peroxide           N02,  v 

Nitric  Anhydride       N^O*         Nitric  Acid  H-0-NO*. 


159.  Nitric  Acid.  HNO&  —  When  electrical  discharges  are 
passed  through  air  which  is  in  contact  with  caustic  or  carbo- 
nated alkalies,  or  when  organic  matter  decays  in  the  atmosphere 
under  the  same  conditions,  a  partial  union  of  the  elements  of  the 
atmosphere  takes  place,  and  nitrates  of  potassium,  sodium,  or 
calcium  are  the  usual  result.  From  either  of  these  native  ni- 
trates, or  nitres,  the  acid  may  be  obtained.  It  is  usually  pre- 
pared by  distillation  from  a  mixture  of  sodic  nitrate  (127)  and 
sulphuric  acid. 

Na-0-N02+ff2=02=S02  =  ff,Na=02=S02+H-0-N02.  [135] 

One  molecule  of  sulphuric  acid  is  adequate  to  decompose  two 
molecules  of  nitre  ;  but  the  temperature  required  is  then  much 
higher,  and  the  nitric  acid  is  in  part  decomposed.  The  strong- 
est acid  thus  prepared  is  a  colorless,  fuming  liquid,  boiling  at  86° 
and  freezing  at  —  49°.  Its  Sp.  Gr.  =  1.552  at  20°.  It  is  un- 
stable, and  is  partially  decomposed  when  exposed  to  the  light. 


4H-0-NO,  =  2H20  +  4N02  +  0-0.        [136] 

The  remaining  acid  is  thus  diluted,  while  the  nitric  peroxide 
colors  it  yellow.  A  similar  decomposition  takes  place  during 
the  distillation  of  the  acid.  This  decomposition  continues  until 
the  hydrate  2HNOS  .  3ff20  is  formed,  which  is  far  more  stable 
and  distils  unchanged  at  123°.  This  is  the  common  strong 
nitric  acid  of  commerce,  but  it  is  not  a  definite  compound,  the 
composition  varying  with  the  pressure  under  which  the  acid 
distils.  A  still  weaker  acid  is  much  used  in  the  arts  under  the 
name  of  aqua-fortis.  The  strength  of  the  acid  may  be  deter- 
mined from  its  specific  gravity  by  means  of  tables  prepared  for 
the  purpose. 


§  159.]  NITROGEN.  235 


Sp.  Gr. 

Per  Cent. 
HNO3 

Sp.  Gr. 

Per  Cent. 
HNO3 

Sp.  Gr. 

Per  Cent 
HNOS 

1.500 

92.98 

1.395 

64.17 

1.228 

36.28 

1.470 

82.71 

1.343 

51.50 

1.165 

26.95 

1.435 

73.10 

1.289 

45.62 

1.105 

17.62 

Nitric  acid  is  one  of  the  most  corrosive  agents  known.  With 
a  very  few  exceptions,  it  oxidizes  all  the  elementary  substances, 
converting  them  into  oxides,  acids,  or  nitrates,  as  the  case  may 
be.  In  these  reactions,  as  a  general  rule,  nitric  oxide  is  evolved; 
but  the  products  vary  to  a  certain  extent  with  the  conditions  of 
the  experiments,  and  examples  will  be  found  under  the  differ- 
ent elements,  and  also  in  [107],  [142],  [151],  and  [156],  illus- 
trating the  different  phases  which  the  reaction  may  assume.  Ni- 
tric acid  corrodes  all  organic  tissues,  oxidizing  them,  and  forming 
various  products,  among  which  the  most  common  are  water, 
carbonic  acid,  and  oxalic  acid.  When  more  dilute,  it  stains  the 
skin,  wool,  silk,  and  other  albuminoid  bodies  of  a  bright  yellow 
color.  Very  strong  nitric  acid,  when  mixed  with  strong  sul- 
phuric acid,  acts  on  some  organic  compounds  in  a  very  remark- 
able way.  It  removes  one  or  more  atoms  of  hydrogen,  and  sub- 
stitutes an  equal  number  of  atoms  of  the  radical  N02  in  their 
place.  (31). 


e  +  H-  0-N02  =  06ff5(N02)  +  H2  0.       [137] 

Benzol.  Nitro-Benzol. 

With  the  various  bases  it  forms  a  large  class  of  important  salts. 

When  the  radical  is  univalent,  these  salts  have  the  general 

i 
symbol  R-0~N02.     When  the  radical  is  bivalent,  the  general 

IT  IT 

formula  becomes  R=0.f(NO^)<^  or  R=OfN20^.  Salts  of  these 
types  are,  in  the  ordinary  use  of  the  term,  the  normal  or  ortho- 
nitrates  ;  but,  theoretically,  nitrogen  is  capable  of  fixing  five 
univalent  radicals,  and  hence  some  chemists  regard  the  assumed 
compound  £T5=05^Nas  orthonitric  acid,  and  salts  of  that  type  as 
orthonitrates.  By  eliminating  from  this  orthoacid  first  one  and 
then  two  molecules  of  water,  we  obtain  the  following  anhydrides, 
the  last  of  which  is  the  ordinary  acid. 

Orthonitric  Acid       H^O^N,       or     H~0-N0.2  .  2ff20, 
Metanitric      «          JfyOfNO,    or     H-0-N02  .  ff20, 
Dimetanitric  "  H- 


236  NITROGEN.  [§161. 

Salts  are  known  whose  symbols  may  be  written  on  all  these 
types,  but  they  may  also  be  written  on  the  ordinary  type  as 
well.  Thus 


or 

Dihydro-bismuthic  Orthonitrate.  Basic  bismuthic  Nitrate. 

[138] 
or     (Mg-0-Mg-0-MgyOf(NOJ)f 

Magnesic  Metanitrate.  Trimagnesic  Nitrate. 

Such  distinctions  are  of  no  practical  importance,  but  they  are 
of  value  in  pointing  out  the  many-sided  relations  of  our  subject 
Under  no  condition  does  potassic  hydrate  form  more  than  one 
salt  with  nitric  acid,  and  the  important  theoretical  bearing  of 
this  fact  is  evident. 

160.  Nitric  Anhydride,  N205,  may  be  obtained  by  passing 
dry  chlorine  gas  over  dried  argentic  nitrate  heated  to  95°. 

4AgN03  +  2  01-  Cl  —  ±AgCl  +  2N205  +  0-0.  [139] 

It  is  a  white  solid,  crystallizing  in  prisms  of  the  fourth  system, 
melting  at  29°.5,  and  boiling  at  45°.  Very  unstable,  undergoing 
spontaneous  decomposition  in  a  sealed  glass  tube.  By  the  ac- 
tion of  water  it  forms  nitric  acid. 


H20  =  2HN03.  [140] 

161.  Nitrous  Anhydride.  N203.  —  Best  prepared  by  the 
action  of  dilute  nitric  acid  (Sp.  Gr.  1.25)  on  starch.  Is  also 
formed  in  the  following  reactions  :  — 


[141] 

N203  +  3Jf20.  [142] 
4S9"©  +  ©=©  =  2N20S.  [143] 

In  each  case  brownish-red  fumes  are  formed,  which,  at  a  low 
temperature,  become  condensed  into  a  very  volatile  blue  liquid, 
boiling  at  about  0°.  With  a  small  quantity  of  water  it  yields 
nitrous  acid,  H-O-NO,  but  a  large  quantity  at  once  decom- 
poses it. 

[144] 


If  the  red  vapor  is  passed  into  a  solution  of  potassic  hydrate, 


§162.]  NITROGEN.  237 

we  obtain  potassic  nitrite,  and  in  a  similar  way  other  nitrites 
may  be  made. 

(2KOff+  Aq)  +  N20S  =  (2K-0-NO  +  ff20+Aq).  [145] 

According  to  the  theory  of  the  last  section,  ordinary  nitrous 
acid  is  the  first  anhydride  of  an  assumed  acid,  H^OfN.  This 
would  be  called  orthonitrous  acid,  and  the  ordinary  acid  would 
then  be  metanitrous  acid.  The  compound  PbzlO&lN2,  accord- 
ing to  this  view,  is  plumbic  orthonitrite,  but  it  may  be  also  re- 
garded as  a  triplumbic  nitrite  of  the  ordinary  type  (Pb-0~Pb- 
0-Pb)=02=(NO)2. 

162.  Nitric  Peroxide,  N02,  is  best  prepared  by  mixing  two 
volumes  of  nitric  oxide  with  one  of  oxygen  gas,  both  absolutely 
dry. 

[146] 


The  two  gases  when  mixed  immediately  combine,  yielding  a 
deep  brownish-red  vapor,  which,  if  passed  into  perfectly  dry 
tubes  cooled  by  a  freezing  mixture,  is  condensed  to  a  crystalline 
solid.  This  solid  melts  at  —  9°  to  an  orange-colored  liquid, 
which  boils  at  22°,  but  when  once  melted  it  does  not  freeze 
even  at  —  20°.  The  substance  is  decomposed  by  water  with 
the  greatest  readiness.  A  mere  trace  of  water  is  sufficient  to 
prevent  the  formation  of  the  crystals,  occasioning  instead  the 
production  of  a  green  liquid,  which  appears  to  be  a  solution  of 
nitrous  anhydride  in  nitric  acid. 

±N02  +  H20  =  2HN03  +  N20S.  [1  47] 

If  a  larger  amount  of  water  is  present,  we  obtain  nitric  oxide 
in  place  of  nitrous  anhydride,  and  the  equation  becomes 

3N02  +  H20  ==  2HNOS  +  NO.  [148] 

In  a  similar  way,  when  acted  on  by  metallic  hydrates  and  basic 
anhydrides,  it  yields  a  mixture  of  nitrate  and  nitrite.  Thus" 

2K-0-H+  2N02  =  K-O-NO  +  K-O-NO,  +  H20.  [149] 

Nitric  peroxide  may  also  be  obtained  by  distilling  plumbic 
nitrate,  — 

0=0.      [150] 


238  NITROGEN.  [§163. 

Owing  to  the  presence  of  a  little  moisture,  we  first  obtain  the 
green  liquid  mentioned  above,  but  towards  the  end  of  the  pro- 
cess the  anhydrous  peroxide  comes  over  and  may  be  crystallized. 
Nitric  peroxide  appears  also  to  be  formed  in  the  reaction  of 
nitric  acid  on  tin,  —  • 


ffw  01QSn505  +  5ff2  0+  20N02;  [151] 

but  in  this,  as  in  other  reactions  of  nitric  acid  on  the  metals, 
the  main  product  is  more  or  less  mixed  with  other  oxides  of 
nitrogen. 

163.   Nitric  Oxide,  NO,  is  best  prepared  by  the  action  of 
dilute  nitric  acid  (Sp.  Gr.  about  1.2)  on  copper-turnings. 


(3Gu(NOs)2  +  ±H,0  +  Aq)  +  2NO.  [152] 

The  reaction  appears  to  consist,  first,  in  a  metathesis  of  the 
metal  with  the  hydrogen  of  the  acid,  and  secondly,  in  the  re- 
duction of  a  further  portion  of  the  acid  by  the  hydrogen  thus 
liberated.  In  order  to  obtain  a  pure  product  it  is  important 
that  the  acid  should  be  in  excess.  Nitric  oxide  may  also  be 
obtained  perfectly  pure  by  heating  together  a  mixture  of  fer- 
rous chloride,  nitre,  and  hydrochloric  acid. 


(QFeCl2  +  ZKNOz  +  SHCl  +  Aq)  = 

2NO.  [153] 


A  mixture  of  ferrous  sulphate,  nitre,  and  dilute  sulphuric  acid 
(Sp.  Gr.  1.18)  may  also  be  used. 

Nitric  oxide  is  a  colorless  permanent  gas  (Sp.  Gr.  =  15), 
but  slightly  soluble  in  water  (one  volume  of  water  dissolves 
one  twentieth  of  a  volume  of  NO).  It  extinguishes  a  burning 
candle,  but  both  phosphorus  and  charcoal,  if  burning  vigorously, 
continue  to  burn,  and  with  great  intensity,  when  plunged  into 
the  gas.  It  is  the  most  stable  of  the  oxides  of  nitrogen,  and  is 
not  decomposed  by  a  red  heat.  It  is  neither  an  acid  nor  a  basic 
anhydride,  but  it  is  marked  by  its  avidity  for  oxygen,  with  which 
it  forms  the  brownish-red  fumes  either  of  N02  or  of  NZ0&  ac- 
cording to  the  proportions  present.  [143]  and  [146].  It  dis- 
solves freely  in  a  solution  of  ferrous  sulphate,  forming  a  deep 
reddish-brown  liquid,  from  which  the  gas  may  be  expelled  by 


§165.]  NITROGEN.  239 

heat.     A  similar  product  may  be  obtained  with  other  ferrous 
salts,  and  this  reaction  may  be  used  as  a  test  for  nitric  acid. 

1  64.   Nitrous  Oxide,  N2  0,  is  best  prepared  by  gently  heating 
ammonic  nitrate  in  a  glass  flask  or  retort, 


NH;  0-N02  =  2ff20  +  N2  0.  [154] 

It  may  also  be  obtained  by  exposing  nitric  oxide  gas  to  the 
action  of  moistened  iron-filings,  which  absorb  one  half  of  the 
oxygen. 

±NO  __  o-O  =  2N20.  [155] 

It  is  also  evolved  when  zinc  dissolves  in  dilute  nitric  acid,  or, 
more  surely,  when  a  mixture  of  equal  parts  of  nitric  and  sul- 
phuric acids,  diluted  with  eight  or  ten  parts  of  water,  is  used  for 
dissolving  the  metal. 

±Zn  +  (WffN03  +  Aq)  = 

(±Zn(N03)2  +  5ff20  +  Aq)  +  N20.  [156] 

Nitrous  oxide  is  a  colorless  gas  (Sp.  Gr.  22),  which,  by  pres- 
sure and  cold,  may  be  condensed  to  a  colorless  liquid,  boiling  at 
—  88°  and  freezing  by  its  own  evaporation  at  about  —  101°. 
It  is  less  stable  than  nitric  oxide.  It  is  decomposed  by  heat, 
and  all  combustibles  burn  in  it  with  nearly  the  same  readiness 
and  brilliancy  as  in  pure  oxygen  gas.  When  pure,  it  can  be  in- 
haled without  danger,  and  is  much  used  as  an  anaesthetic  agent. 
With  some  patients  it  produces  at  first  a  transient  intoxication, 
attended  at  times  with  uncontrollable  laughter.  Hence  the  pop- 
ular name  of  laughing-gas.  It  manifests  no  tendency  to  unite 
with  more  oxygen.  It  is  soluble  in  water  to  a  limited  extent, 
and  to  a  much  greater  degree  in  alcohol.  At  0°  one  volume  of 
water  dissolves  1.3  volumes,  and  one  volume  of  alcohol  4.18 
volumes,  of  this  gas. 

165.  Oxychlorides  of  Nitrogen.  —  If  in  reaction  [111]  no 
gold  or  other  metal  is  present  to  unite  with  the  chlorine  evolved 
by  the  aqua-regia,  this  element  combines  with  the  nitric  oxide 
set  free  at  the  same  time,  and  besides  chlorine  gas  we  obtain,  as 
products  of  the  reaction,  two  compounds  which  we  may  call  ni- 
trous oxychloride  and  nitric  oxydichloride  respectively. 


Aq)  +  NOCl  +  Cl-Cl  [157] 


240  NITROGEN  [§166. 


or      (2HNOS  +  GffCl  +  Aq)  = 

(4Hi  0  +  Aq)  +  2NOC12  +  Cl-d  [158] 

During  the  early  stages  of  the  decomposition  of  aqua-regia  the 
second  of  the  two  reactions  prevails,  and  the  product  is  nearly 
pure  NO  Olz  '•>  Dut  as  tne  process  advances  this  becomes  more 
and  more  mixed  with  NO  01  At  the  ordinary  temperature 
both  substances  are  gases,  NO  Cl  having  an  orange,  and  NO  C12 
a  deep  lemon-yellow  color  ;  but  by  cold  they  may  be  readily 
condensed  to  liquids,  which  have  a  red  color  and  resemble  each 
other  in  odor  and  aspect.  They  have  neither  acid  nor  basic 
relations,  but  are  readily  decomposed  by  chemical  agents  into 
nitric  oxide  and  chlorine  ;  and  by  mixing  together  these  two 
gases  the  same  or  similar  compounds  may  be  reproduced.  By 
the  action  of  dry  hydrochloric  acid  on  anhydrous  nitric  perox- 
ide, still  a  third  compound  is  formed,  which  has  the  symbol 
N0%  Cl,  and  resembles  the  other  two.  The  last  compound  may 
also  be  obtained  by  mixing  phosphoric  oxytrichloride  with 
plumbic  nitrate. 

3Pb=Of(N02)2+2POCl3=Pl>sW<M(PO)2+GN02CL  [159] 

166.  Compounds  with  Hydrogen.  —  Ammonia  Gas.  NH8. 
—  Nitrogen  and  hydrogen  gases  will  not  directly  combine  ;  but 
through  various  indirect  methods,  not  well  understood,  this 
union  is  constantly  taking  place  in  nature,  and  ammonia  gas  is 
the  chief  product.  This  gas,  or  some  one  of  its  numerous  com- 
pounds, is  constantly  formed  whenever  an  organic  substance 
decays  or  is  charred,  as  in  the  process  of  dry  distillation.  It  is 
also  formed  in  many  chemical  reactions  when  nitrogen  and  hy- 
drogen atoms  are  brought  together  at  the  moment  of  chemical 
change.  Thus  when  a  mixture  of  nitric  oxide  and  hydrogen 
gas  is  passed  over  heated  platinum  sponge,  we  have  the  reaction 


2NO  +  5H-H—  2H,  0  +  2  JV773.  [1  60] 

So  also  when  nitric  acid  is  added  in  very  small  quantities  at  a 
time  to  a  mixture  of  zinc  and  dilute  hydrochloric  acid,  from 
which  hydrogen  gas  is  being  slowly  evolved,  we  have  the  re- 
action 

[161] 


§166.]  NITROGEN.  241 

But  the  ammonia  thus  produced  unites  at  once  with  the  hydro- 
chloric acid  present  to  form  ammonic  chloride,  and  in  a  similar 
way  ammonia  salts  are  frequently  formed  to  a  limited  extent 
when  zinc  and  similar  metals  are  dissolved  in  nitric  acid.  Prac- 
tically, we  always  prepare  ammonia  gas  from  the  commercial 
ammonic  chloride  by  the  reaction 


-f  Ga-02=ff2  =  CaCl2  +  2ff20  +  2Nff3.  [162] 


It  is  a  colorless  gas,  so  light  (0p.  (St.  0.591)  that  it  can  be 
collected  in  an  inverted  bottle  by  displacement.  By  pressure 
and  cold  it  may  be  readily  condensed  to  a  liquid,  which  boils  at 
—  38°.  5  and  freezes  at  —  75°.  The  evaporation  of  the  lique- 
fied gas  is  attended  with  great  reduction  of  temperature,  and 
this  principle  is  applied  in  the  apparatus  of  Carre  to  the  artifi- 
cial production  of  cold.  Ammonia  has  a  familiar  pungent  odor, 
and  is  useful  in  medicine  as  an  irritant,  but  when  pure  it  is 
wholly  irrespirable.  It  is  incombustible  in  air,  but  burns  in  an 
atmosphere  of  oxygen,  yielding  aqueous  vapor  and  nitrogen  gas. 

The  composition  of  ammonia  gas  may  be  thus  ascertained: 
First,  by  passing  a  series  of  electrical  discharges  through  a 
confined  volume  of  the  gas  in  a  eudiometer  the  volume  doubles. 


2Nff3  =  N-=N+  3ff-ff.  [163] 

If  next  we  add  to  this  product  one  half  of  its  volume  of  oxygen 
gas,  then  explode  the  mixture,  and  subsequently  remove  with 
pyrogallic  acid  the  residual  oxygen,  we  shall  find  that  the  vol- 
ume of  nitrogen  gas  remaining  in  the  tube  is  exactly  one  half 
of  the  volume  of  the  ammonia  gas  with  which  we  started.  Sec- 
ondly, if  we  shake  up  in  an  eudiometer-tube  a  measured  vol- 
ume of  chlorine  gas  with  a  weak  solution  of  aqua  ammonia, 
taking  care  after  the  reaction  is  finished  to  expel  by  heat  all  the 
nitrogen  from  the  liquid,  it  will  be  found  that  the  volume  of 
chlorine  has  been  replaced  by  one  third  of  its  volume  of  nitro- 
gen gas. 

With  colored  test-paper  ammonia  gas,  even  when  dry,  gives 
a  strong  alkaline  reaction,  and  it  directly  combines  with  several 
of  the  acid  anhydrides.  These  unimportant  compounds,  however, 
must  not  be  confounded  with  the  important  class  of  ammonia 
salts.  In  part  they  correspond  to  the  amides  mentioned  below, 
11  p 


242  NITROGEN.  [§167. 

but  the  constitution  of  others  is  not  well  understood.  The  last 
are  frequently  called  ammonides,  and  of  these  sulphuric  aramon- 
ide  (Nffs)2  •  SO&  will  serve  as  an  example.  Ammonia  gas 
forms  also  equally  anomalous  compounds  with  many  anhydrous 
metallic  salts.  Thus,  argentic  and  calcic  chlorides  absorb  large 
volumes  of  ammonia  gas,  forming  what  appear  to  be  molecular 
compounds,  Ag  Cl  .  2ff3N  and  Ga  C12  .  SH3N,  in  which  the  am- 
monia seems  to  play  somewhat  the  same  part  as  water  of  crys- 
tallization in  ordinary  salts.  But  by  far  the  most  important 
quality  of  ammonia  is  its  power  of  combining  directly  with 
water  and  with  the  acids,  as  such,  to  form  the  large  class  of 
ammonia  salts.  In  forming  these  compounds,  however,  nitro- 
gen changes  its  quantivalence,  and  it  will  therefore  be  conven- 
ient to  class  them  under  a  different  head.  When  ammonia  gas 
comes  in  contact  with  the  fumes  of  a  volatile  acid,  the  formation 
of  the  ammonia  salt  gives  rise  to  a  dense  white  smoke,  which  is 
one  of  the  most  characteristic  tests  for  this  substance. 

167.  Amines  or  Compound  Ammonia.  —  Ammonia  gas  is 
the  type  of  a  large  class  of  compounds,  most  of  them  volatile, 
in  all  of  which  nitrogen  is  trivalent.  These  compounds  may  be 
regarded  as  derived  from  one  or  more  molecules  of  ammonia 
by  replacing  the  hydrogen  atoms  either  wholly  or  in  part  with 
various  positive  radicals.  According  as  they  are  fashioned 
after  the  type  of  one,  two,  three,  or  more  molecules  of  ammonia 
they  are  called  monamines,  diamines,  &c.,  and  they  are  distin- 
guished as  primary,  secondary,  or  tertiary,  according  as  one, 
two,  or  three  hydrogen  atoms  in  the  monamines,  or  the  corre- 
sponding groups  of  atoms  in  the  polyamines,  have  been  replaced. 
We  may  represent  the  type  of  ammonia  either  as  in  (29),  or 
more  graphically  in  the  vertical  form  as  in  table  below,  which 
contains  the  symbols  of  a  few  of  the  compound  ammonias. 

Monamines. 

Primary.  Secondary.  Tertiary. 


H)  OH.)         C6tf5)  CZH 

H[N      H\-N     H[N     C,H 

H)  H)  H)  H 


H  )  C6H6 ) 

Ammonia.     Methylamine.    Phenylamine.       Diethylamine.      Phenylethyl-      Methyl  ethyl- 
(Aniline.)  amine.  phenylamme. 


§168.]  NITROGEN.  243 

Diamines. 

Primary.    •  Tertiary. 


H,-) 

tr- 


Ammonia.  Ethylene  diamine.  Diethylene-diethyl-diamine. 

Doubly  condensed. 

Many  of  the  ammoniated  compounds  of  the  metals  may  be  ar- 
ranged under  this  same  type.  Thus,  when  potassium  is  heated 
in  dry  ammonia  gas,  an  olive-green  compound  is  formed,  which 
has  the  composition  KjUjHtfTq  and  other  examples  will  be 
given  hereafter. 

The  amines  are  all  basic,  and  like  ammonia  gas  combine  di- 
rectly with  acids  to  form  salts ;  but  this  character  is  the  less 
strongly  marked  in  proportion  as  the  hydrogen  atoms  have  been 
replaced.  The  volatile  organic  bases  belong  to  the  same  class 
of  compounds. 

168.  Amides.  —  The  atoms  of  hydrogen  in  ammonia  gas 
may  be  replaced  by  negative  as  well  as  by  positive  radicals ; 
but  then  the  product,  instead  of  being  basic,  is  either  neutral 
or  acid.  They  are  classified  and  named  like  the  amines,  but 
with  few  exceptions  only  one  or  one  set  of  the  hydrogen  atoms 
can  be  thus  replaced.  The  folio  whig  are  a  few  examples :  — 

Monamides.  Diamides. 


H\N 
H 

Acetamide.  Benzamide.  Oxamide.  Succinamide. 

These  compounds  may  also  be  regarded  as  formed  by  the  union 
of  the  compound  radical  amidogen  (HZN)  with  the  acid  radical, 
and  hence  the  name  amides.  They  differ,  then,  from  the  cor- 
responding acids  only  in  containing  amidogen  in  place  of  hy- 
droxyl.  Thus, 

ffo-C2ff30,         HofCO,          HofCzOft          HofGJJ^O^ 

Acetic  Acid.  Carbonic  Acid.  Oxalic  Acid.  Succinic  Acid. 


ide  (Urea  ?).  Oxamide.  Succinamide. 


244  NITROGEN.  [§168. 

These  amides  are  all  neutral  ;  but  if  in  the  dibasic  acids  we  re- 
place only  one  of  the  atoms  of  hydroxyl,  it  is  evident  that  we 
shall  obtain  a  class  of  amides  still  containing  an  atom  of  basic 
hydrogen,  and  which  are,  therefore,  acids.  Thus  are  formed 


HO,H2N=CO.  ,2, 

CarbamicAcid.1^  Oxamic  Acid.  Succinamic  Acid. 

+         — 

Lastly,  if  we  take  an  acid  like  lactic  acid,  HO,HO=CzH±0,  or 

gly  collie  acid,  JIO,ffO=C2ff20,  which,  although  diatomic,  is 
only  monobasic  (43),  we  can  obtain  from  each  acid,  at  least 
theoretically,  two  distinct  amides,  according  as  we  replace  the 

basic  hydrogen  (H)  or  the  alcoholic  hydrogen  (ff),  see  (43). 
The  first  will  be  neutral,  the  second  acid  ;  but  although  several 
of  the  acid  amides  are  known,  the  only  neutral  amide  of  this  class 
which  has  been  investigated  is  that  derived  from  lactic  acid. 

NK2,HO=Csff<0,         ffO,Nff2=C3ff40,         ffO,Nff2=C2ff20. 

Lactamide  (Neutral).  Lactamide  (Acid).         Glycolamide  (Acid)  or  Glycocoll. 

From  these  various  amides  a  large  number  of  compounds 
may  be  derived  by  replacing  the  hydrogen  atoms  either  of  the 
amidogen  or  of  the  acid  with  different  compound  radicals.  The 
following  are  a  few  examples  :  — 

07ff50)  0202    )  ((C2ff6)0-C202)) 

C6H5\N         (G2H5},\N2  H\N 

H)  HJ  ff) 

Phenyl-benzamide.  Diethyl-oxamide.  Oxamethane. 

H0-C2ff2  0  )         HO-  C3ff4  0  )          (  C2ff5)  0-C3fft  0  ) 
G7H50\N  G2H5\N  H\N 

H)  H)  H) 

Hippuric  Acid.  Lactethylamide.  Lactmethane. 

The  last  two  compounds  are  isomeric,  the  only  difference  being 
that  in  the  first  the  radical  ethyl  replaces  an  atom  of  hydrogen 
of  the  amidogen,  while  in  the  second  it  replaces  the  alcoholic 
hydrogen  of  the  lactic  acid.  That  there  is  a  real  difference 
between  the  two  is  proved  by  the  following  reactions  :  — 

H 


ff)  Potasslc  Ethyl-lactate.  ff 

1  The  acid  has  not  been  isolated,  but  the  ammonic  salt  is  well  known. 


§171.]  NITROGEN.  245 


Potassic  Lactate.  fj  ) 

Ethylamine. 

These  complex  amide  compounds  may  also  be  referred  to  a 
system  of  mixed  types.  (Compare  30,  Part  I.) 

169.  Imides.  —  If  from  an  acid  monamide  we  eliminate  a 
molecule  of  water,  or  if  from  a  neutral  diamide  we  eliminate  a 
molecule  of  ammonia  gas,  we  obtain  as  the  product  a  compound 
which  may  be  regarded  as  formed  by  the  union  of  the  acid  rad- 
ical with  the  compound  radical  HN.  Thus, 


=  H-0-H+  HN-  C3H4  0.     [1  66] 

e.  Lact-imide. 

04H4  02  =  ff3N  +  HN-  C4H4  02.        [167] 

Succin-amide.  .  Succin-imide. 

Such  compounds  are  called  Imides,  and  they  always  act  as 
monobasic  acids. 

170.  Nitriles.  —  If  from  a  neutral  monamide  we  eliminate 
a  molecule  of  water,  the  residue,  which  may  be  regarded  as  a 
compound  of  nitrogen  with  a  trivalent  radical,  has  been  called 
a  Nitrik.  Thus, 

.  [1  68] 


=  H20  +  C5H,-=N.  [169] 

Valeramide.  Valeronitrile. 

These  compounds  are  weak  bases,  like  ammonia,  combining  di- 
rectly with  acids  to  form  salts,  and  they  may  be  regarded  as  a 
part  of  the  class,  of  amines. 

171.  Ammonium  Compounds.  —  In  all  the  above  compounds 
nitrogen  is  trivalent,  and  a  single  atom  of  this  element,  unas- 
sisted, does  not  appear  to  be  able  to  hold  together  more  than 
three  atoms  of  hydrogen  or  of  other  univalent  positive  radicals  ; 
but  when  the  different  ammonias  are  brought  in  contact  with 
acids,  the  nitrogen  atoms  suddenly  manifest  two  additional  af- 
finities, and  a  most  important  class  of  compounds  is  formed, 
in  which  nitrogen  is  quinquivalent.  The  cause  of  this  sudden 
accession  of  power  is  not  well  understood,  but  it  evidently  de- 


246  NITROGEN.  [§171. 

pends  on  the  reflex  influence  which  the  negative  atoms  or  rad- 
icals of  the  acids  exert.  In  all  these  cases  the  ammonias  com- 
bine with  the  acids  as  a  whole,  and  the  reaction  is  an  example 
of  synthesis  and  not  of  metathesis.  The  following  are  a  few 
examples :  — 


+  HGl  =  mHv  Gl  =  NH4  Gl      like        KCL  [170] 

Ammonic  Chloride. 

like  K-  0-H.  [171] 


Ammonic  Hydrate 

+ 


like  K-O-NO*  [172] 

Ammonic  Nitrate. 

(N-=ff3)2  +  HfSOt  =  N2*ff8,(S04)  = 

(NH4)fOfS02  like  KfOfSO*  [173] 

Ammonic  Sulphate. 

The  products  thus  obtained  resemble  very  closely  the  salts  of 
the  alkaline  metals.  With  certain  limitations  they  are  suscep- 
tible of  the  same  reactions,  and  in  these  reactions  the  atomic 
group  NH4  plays  the  same  part  as  the  metallic  atoms  in  the 
other  salts.  Thus  we  have 

(Ag-N03  +  NH4Gl  +  Aq)  = 

AgGl  +  (Nff4-N03  +  Aq).  [174] 

(GaCl2  +  (NffJfOfCO  +  Aq)  = 

Ga-OfCO  +  (2Nff4Cl+Aq).  [175] 

Hence  we  conclude  that  the  ammonia  salts  are  compounds  of 
this  univalent  radical  which  we  call  ammonium,  and  therefore 
we  write  their  symbols  as  above.  But  although  many  attempts 
have  been  made  to  obtain  the  radical  substance  corresponding 
to  Nff4,  these  attempts  have  been  hitherto  unsuccessful.  It  is 
true  that  when  we  electrolyze  a  solution  of  ammonic  chloride, 
using  as  the  negative  pole  of  the  battery  a  quantity  of  mercury, 
we  obtain  a  material  resembling  a  metallic  amalgam,  which, 
when  kept,  slowly  changes  back  to  metallic  mercury,  evolving 
a  mixture  of  hydrogen  and  nitrogen  gases ;  but  it  would  now 
appear  that  in  this  pasty  mass  the  gases  are  merely  mixed,  and 
not  chemically  combined,  and,  moreover,  the  total  amount  of 


§173.]  NITROGEN.  247 

material  which  the  mercury  thus  singularly  encloses  is  exceed- 
ingly small. 

172.  Ammonic  Chloride   (Sal  Ammoniac),  NJI4Cl,  is   the 
most  important  of  the  ammonia  salts,  and  the  material  from 
which  the  other  ammonia  compounds  are  prepared.     It  is  man- 
ufactured in  large  quantities  from  the  ammoniacal  liquid  of  the 
gas-works,  one  of  the  products  of  the  dry  distillation  of  coal. 
It  is  a  white  crystalline  salt,  very  soluble  in  water,  but  only 
slightly  soluble  in  alcohol.     It  sublimes  below  redness  without 
first  melting.     It  is  isomorphous  with  sodic  and  potassic  chlo- 
ride, and  resembles  these  salts,  especially  the  last,  very  closely. 
Like  potassic  chloride,  it  is  precipitated  from  aqueous  solutions 
by  platinic  chloride,  with  which  it  forms  a  double  salt  insoluble 
in  water. 

(2NfftCl  +  PtClt  +  Aq)  =  (Nff4Cl)2.PtClt  +  (Aq).  [176] 

173.  Ammonic  Hydrate  (Aqua  Ammonia).    (NH^O-H  -\- 
Aq.)  —  At  0°  water  absorbs  1,050  times  its  own  volume  of  am- 
monia gas,  but  the  quantity  absorbed  rapidly  diminishes  as  the 
temperature  rises,  so  that  at  15°  it  can  only  hold  727  times  its 
volume,  and  at  24°  600  times  its  volume.     Water  saturated  at 
15°  contains  about  one  third  of  its  weight  of  ammonia,  but  in 
consequence  of  the  great  expansion  which  attends  the  absorp- 
tion, the  solution  is  lighter  than  water.     This  solution  has  the 
pungent  odor  of  ammonia,  because  the  gas  slowly  escapes  even 
at  the  ordinary  temperature  of  the  air,  and  by  prolonged  boiling 
the  whole  may  be  driven  off.     In  this  and  in  other  physical  re- 
lations the  compound  of  ammonia  with  water  acts  like  the  solu- 
tion of  a  gas,  but  in  all  its  chemical  relations  it  behaves  like  an 
alkaline  hydrate.     It  is  strongly  caustic ;  it  precipitates  metallic 
hydrates  from  solutions  of  their  salts,  and  is  very  much  used  in 
the  laboratory  as  an  alkaline  reagent.     It  has  been  called  the 
volatile  alkali.     It  differs,  however,  from  the  Jixed  alkalies,  soda, 
and  potassa,  in  two  important  particulars.     First,  it  is  decom- 
posed by  heat  into  ammonia  gas  and  water,  and  is  not,  therefore, 
properly  speaking,  volatile.     Secondly,  it  forms  with  many  me- 
tallic radicals  soluble  double  salts,  and  other  compounds  of  pecu- 
liar constitution,  which  can  have  no  counterparts  among  the  com- 
pounds of  the  alkaline  metals.     Hence  it  is  that  in  many  im- 
portant particulars  the  reactions  of  the  ammonia  salts  are  wholly 


248  NITROGEN.  [§  174. 

different  from  those  of  the  corresponding  salts  of  sodium  and 
potassium.  They  either  do  not  give  precipitates  under  the 
same  conditions,  or  the  precipitates  obtained  have  a  wholly  dif- 
ferent character.  Compare  [174],  [175],  with  (265),  (276), 
and  (316). 

174.  Ammonic  Carbonate.  —  The  commercial  salt  is  a  trans- 
lucent white  solid,  obtained  by  subliming  a  mixture  of  sal-am- 
moniac with  chalk.     It  is  very  soluble  in  water,  has  the  odor 
of  ammonia,  and  a  strong  alkaline  reaction.     Its  composition  is 
not  unvarying,  but  the  usual  product  appears  to  be  a  mixture 
of  hydro-ammonic  carbonate  and  ammonic  carbamate  (168)  in 
equivalent  proportions.     Exposed  to  the  air  it  loses  about  44 
per  cent  of  its  weight,  owing  to  the  dissipation  of  the  ammo- 
nic carbamate,  which  is  resolved  into  C0.2  and  JVZ^,.and  the 
opaque  spongy  residue  consists  of  hydro-ammonic  carbonate. 
From  the  commercial  salt  there  may  be  prepared  well-defined 
crystals  of  the  three  following  compounds :  — 

Acid  or  Hydro-ammonic  Carbonate      H.NH^O=CO. 
Neutral  or  Diammonic  Carbonate          (JV7/4),=0a=C0  .  H20. 
Dihydro-tetra  ammonic  Tricarbon ate   Hz.(NH^^O^'l(CO^  .  HZ0. 

A  solution  of  the  neutral  salt  prepared  by  mixing  a  solution 
of  the  commercial  substance  with  the  requisite  amount  of  aqua 
ammonia  is  very  much  used  in  the  laboratory  as  a  reagent. 

175.  Characteristic  Reactions   of  the   Ammonia    Salts.  — 
These  compounds,  when  heated  with  caustic  alkalies  or  alkaline 
earths,  give  off  ammonia  gas,  which  may  be  recognized  by  its 
odor,  or  by  the  cloud  it  forms  with  HCL     The  ammonia  salts 
are  all  volatile  at  a  moderate  temperature  (except  in  the  few 
cases  in  which  the  acid  is  fixed),  and  are  thus  readily  distin- 
guished from  those  of  the  non-volatile  bases.     This  quality  is 
of  great  importance  in  chemical  analysis,  and  leads  us  to  select 
the  ammonia  salts,  whenever  it  is  possible,  as  reagents,  because 
the  excess  of  the  reagent  and  all  the  ammoniacal  products  can 
so  readily  be  eliminated  by  heat. 

176.  Ammonium  Bases.  — The  salts  formed  by  the  union 
of  the  compound  ammonias,  or  amines,  with  acids,  closely  re- 
semble those  of  ammonia,  and  may  be  regarded  as  consisting  of 
radicals  derived  from  ammonium  by  replacing  one  or  more  of 
its  hydrogen  atoms  with  other  positive  radicals.    ( Of  these  com- 


§  176.]  NITROGEN.  249 

pounds  the  most  interesting  are  those  corresponding  to  ammonic 
hydrates,  but  in  which  all  four  of  the  hydrogen  atoms  have  been 
thus  replaced.  They  may  be  prepared  from  the  ternary  amines 
in  a  manner  which  is  illustrated  by  the  following  reactions:  — 


JV  + 

Triethylamine. 


Iodide  of  Tetrathyl-ammonium. 


-]-0-ff).  [178] 

The  solutions  of  the  amines  in  water,  although,  like  aqua 
ammonia,  they  may  be  regarded  as  compounds  of  an  ammo- 
nium radical,  are  decomposed  when  evaporated  into  the  volatile 
amine  and  water,  and  it  might  have  been  anticipated  that  the 
hydrate  of  tetrathyl-ammonium  would  break  up  in  a  similar  way, 
but  such  is  not  the  case.  This  compound  is  stable,  and  on 
evaporating  the  solution  resulting  from  the  last  reaction  the 
hydrate  is  obtained  as  a  white  solid  resembling  caustic  potash. 
It  absorbs  water  and  carbonic  acid  from  the  air  ;  it  precipitates 
the  metallic  oxides  from  their  salts  ;  it  saponifies  fats,  and  it 
neutralizes  the  strbngest  acids,  just  as  potash  does.  Several 
similar  compounds  have  been  prepared;  and  since  it  appears 
that  the  four  hydrogen  atoms  of  ammonium  may  be  replaced 
by  the  same  or  by  different  atoms  at  will,  it  is  evident  that  an 
infinite  number  of  such  compounds  are,  theoretically  at  least, 
possible.  These  hydrates  have  a  bitter  taste,  and  cannot  be 
volatilized  without  decomposition.  In  both  of  these  particulars 
they  very  closely  resemble  the  non-volatile  organic  alkaloids, 
which  are  evidently  formed  after  the  same  type.  There  are, 
therefore,  two  classes  of  bases  derived  from  ammonia  ;  the  one 
volatile,  after  the  type  of  H%N  ';  the  other  non-volatile,  after  the 
type  of  NHfO-H;  and  corresponding  to  these  there  are  two 
classes  of  organic  alkaloids,  the  first  volatile  like  nicotine  and 
conine,  the  second  non-volatile  like  quinine.  and  morphine.  In 
all  these  bases  the  parts  are  grouped  around  one  or  more  atoms 
of  nitrogen,  and  the  difference  between  the  two  classes  of  com- 
pounds depends  primarily  on  the  fact  that  these  atoms  are  tri- 
ll* 


250  PHOSPHORUS.  [§  177. 

valent  in  the  first  class  and  quinquivalent  in  the  second.  The 
two  classes  of  compounds  are,  however,  intimately  related,  and 
may  be  regarded  from  different  points  of  view.  Thus  the 
amides,  irnides,  and  nitriles,  which  we  have  considered  as  formed 
after  the  type  of  ammonia  gas,  may  also  be  regarded  as  anhy- 
drides of  the  salts  of  the  ammonium  radicals,  and  in  many  cases 
may  be  prepared  from  these  salts  by  a  simple  process  of  dehy- 
dration. Moreover,  careful  study  will  open  up  many  other  re- 
lations of  these  bodies,  all  of  which  must  be  considered  before 
we  can  command  a  comprehensive  view  of  the  subject. 

177.  Chloride  of  Nitrogen,  NCI&  is  a  very  volatile,  yellow, 
oily  liquid,  obtained  by  the  action  of  chlorine  gas  on  a  strong 
solution  of  sal-ammoniac. 

178.  Bromide  of  Nitrogen,  NBr$,  is  obtained  by  digesting 
bromide  of  potassium  with  chloride  of  nitrogen,  and  is  similar 
to  the  last  in  appearance,  but  has  a  much  darker  color. 

179.  Iodide  of  Nitrogen,  NI3,  is  a  black  powder,  formed 
when  aqua  ammonia  is  added  in  large  excess  to  an  alcoholic 
solution  of  iodine.     They  are  all  three  highly  explosive,  and 
illustrate  in  a  most  marked  manner  the  instability  of  all  the 
compounds  of  nitrogen. 

180.  PHOSPHORUS.  P—  31.  —  Found  in  nature,  chiefly 
in  combination  with  calcium,  in  calcic  phosphate,  a  mineral  sub- 
stance very  widely  but  sparingly  disseminated,  and  an  essential 
but  subordinate  constituent  of  many  plants,  and  of  all  the  higher 
animal  structures.     In  order  to  obtain  the  elementary  substance, 
the  calcic  phosphate  (generally  bone  ashes)  is  first  partially  de- 
composed with  sulphuric  acid.    The  soluble  acid  calcic  phosphate 
thus   obtained  is   easily   separated  from  the   nearly  insoluble 
calcic  sulphate,  by  filtration.     The  solution  is  then  evaporated, 
the  acid  phosphate  mixed  with  pulverized  charcoal,  and  the 
thoroughly  dried  mass  distilled  in  earthen  retorts.     The  distil- 
lation proceeds  slowly,  and  requires  a  very  high  temperature. 

<7a3!<96!(P6>)2  +  2fff02=S02  = 

2Ca-02=S02  -f 

When  dried,  ff4,CaWi=(PO)2  =  Ca= 02=(P02)2 
3Ca=02=(P02)2  +  C10  =  CasW^(PO 

181.  Common  Phosphorus,  P4,  when  perfectly  pure,  is  a 


§182.]  PHOSPHORUS.  251 

colorless,  transparent  solid,  but  ordinarily  it  has  a  yellowish  tint, 
and  is  only  translucent.  At  low  temperatures  it  is  brittle,  but 
at  20°  it  is  soft  like  wax.  It  melts  at  45°,  and  boils  at  290°. 
Sp.  Gr.  of  solid  1.83.  Insoluble  in  water,  slightly  soluble  in 
alcohol  and  ether,  still  more  soluble  in  both  the  fixed  and  vola- 
tile oils,  and  very  soluble  in  sulphide  of  carbon  or  chloride  of 
sulphur.  Phosphorus  is  by  far  the  most  combustible  of  the 
chemical  elements.  It  takes  fire  below  the  boiling  point  of 
water,  and  slowly  combines  with  the  oxygen  of  the  air  at  the 
ordinary  temperature.  If  in  not  too  small  quantity,  the  heat 
evolved  by  its  slow  combustion  soon  raises  the  temperature  to 
the  point  of  ignition,  and  it  is  therefore  always  preserved  under 
water  or  alcohol.  The  product  of  the  rapid  combustion  is 
phosphoric  anhydride ;  that  of  the  slow  combustion  in  moist 
air  chiefly  phosphorous  acid.  Exposed  to  the  air  in  the  dark, 
phosphorus  emits  a  greenish  light,  and  hence  its  name,  from 
(j>a>s  (f>opbs ;  but  this  phosphorescence,  though  always  accompany- 
ing the  slow  combustion,  does  not  appear  to  be  necessarily  con- 
nected with  it.  Sticks  of  phosphorus,  when  kept  under  water, 
become  covered  after  some  time  with  a  white  crust,  which  con- 
sists of  a  mass  of  microscopic  crystals ;  and  in  the  course  of 
many  years  these  crystals  may  acquire  considerable  size.  The 
form  of  the  crystals  is  the  regular  dodecahedron  of  the  first  sys- 
tem (Fig.  6),  and  crystals  of  the  same  form  are  obtained  by 
slowly  evaporating  the  solution  of  phosphorus  in  sulphide  of 
carbon. 

182.  Red  Phosphorus.  —  Exposed  to  the  direct  sunlight 
under  water,  phosphorus  becomes  covered  with  a  red  coating, 
and  the  same  red  modification  is  formed  in  great  abundance 
when  ordinary  phosphorus  is  heated  for  several  hours  to  a 
temperature  below  235°  and  250°  in  an  atmosphere  of  carbonic 
anhydride,  or  some  other  inert  gas.  Red  phosphorus  is  insol- 
uble in  carbonic  sulphide,  and  is  thus  easily  separated  from  the 
portion  which  has  not  been  changed.  Iodine  facilitates  the  con- 
version, and  if  a  solution  of  phosphorus  in  sulphide  of  carbon, 
containing  a  little  iodine,  is  sealed  up  in  a  glass  flask  and  heated 
for  some  time  to  only  100°,  red  phosphorus  is  slowly  precipi- 
tated. As  usually  obtained,  red  phosphorus  is  an  amorphous 
powder ;  but  it  has  been  crystallized,  and  it  appears  that  the 
crystals  are  rhombohedrons  belonging  to  the  third  system. 


252  PHOSPHORUS.  [§  183. 

Hence  phosphorus  is  dimorphous,  and  in  this  respect  resembles 
arsenic  and  antimony.  The  Sp.  Gr.  of  red  phosphorus  is  about 
2.1.  It  undergoes  no  change  in  dry  air,  and  may  even  be 
heated  to  250°  without  taking  fire ;  but  at  a  slightly  higher 
temperature  it  changes  back  to  common  phosphorus  and  in- 
flames. The  specific  heat  of  red  phosphorus  is  0.1700,  while 
that  of  the  ordinary  variety  is  0.1387  ;  and  hence,  as  we  should 
anticipate,  this  reverse  change  is  attended  with  the  evolution  of 
heat.  Moreover,  the  calorific  power  of  common  phosphorus  is 
to  that  of  red  phosphorus  in  the  proportion  of  1.15  to  1.  In 
general,  red  phosphorus  is  less  active,  chemically,  than  common 
phosphorus,  and  is  not,  like  the  latter,  poisonous.  Both  varie- 
ties are  largely  used  in  the  manufacture  of  friction-matches. 
The  red  variety  is  not  used  in  making  the  match  itself,  but 
only  in  the  preparation  of  the  surface  on  which  it  is  rubbed. 
183.  Phosphorus  and  Oxygen.  —  The  following  compounds 
of  phosphorus  with  oxygen,  or  with  both  oxygen  and  hydrogen, 
have  been  observed :  — 

Phosphorous  Anhydride  P^O^ 

Phosphoric  Anhydride  P^.0^ 

Hypophosphorous  Acid  H-Q-(P^O,H£), 

Phosphorous  Acid  ff2=Of(P=0,H), 

Orthophosphoric  Acid  Ify03=(P=0), 
Metaphosphoric  Acid  H~0-(P^  02) , 

Pyrophosphoric  Acid  HfOf(P=OfP), 

Sodium  salt  of  Hexabasic  Acid  Na6W6l(P=  02=P-=  0/P--  02=P), 

Sodium  salt  of  Dodecabasic  Acid  Na^  ™  0^  *n.  (PIQ  019) . 

The  relations  of  these  compounds  will  be  best  understood 
by  taking  as  our  first  starting-point  an  assumed  compound, 
JI5i05^P,  in  which  the  atoms  of  phosphorus  are  united  to  hy- 
droxyl  by  all  their  five  affinities.  Ortho1  and  metaphosphoric 
acids  are  now  simply  the  successive  anhydrides  of  this  pent- 
atomic  acid.  Starting  next  from  the  double  molecule  of  our 
assumed  compound,  the  following  anhydrides  are  possible :  — 

ff^O^P,,  3d. 

1st.      J78viii08viii(p-0-P),  4th. 

2d.          H6W^(P=OfP),  5th. 

1  The  assumed  pentatomic  acid  is  by  some  called  orthophosphoric. 


§  186.]  PHOSPHORUS.  253 

Of  these  possible  compounds  the  second  and  fourth  are  identical 
with  ortho  and  meta-phosphoric  acids,  of  which  the  symbols  rep- 
resent two  molecules,  while  the  third  and  the  fifth  are  the  pyro- 
phosphoric  acid  and  phosphoric  anhydride  of  the  above  list. 
The  first  anhydride  of  this  series  has  not  yet  been  observed. 
In  like  manner  we  may  take  three,  four,  or  more  molecules  of 
the  first  compound,  and  deduce  from  each  of  these  condensed 
molecules  another  series  of  anhydrides  ;  but  of  the  infinite  num- 
ber of  compounds  thus  possible,  only  the  salts  of  the  hexabasic 
and  dodecabasic  acid  mentioned  above  are  known.  This  scheme, 
however,  does  not  include  hypophosphorous  and  phosphorous 
acids,  which  have  an  anomalous  constitution.  They  may  be 
regarded  as  orthophosphoric  acids  in  which  atoms  of  hydroxyl 
(two  in  the  first  case  and  one  in  the  second)  have  been  replaced 
with  atoms  of  hydrogen.  The  molecules  of  both  acids  contain 
three  atoms  of  hydrogen,  but  the  first  is  only  monobasic  and  tf  ' 
second  dibasic ;  and  this  fact  illustrates  an  important  principle. 
In  ail  the  so-called  oxygen  salts,  only  those  atoms  of  hydrogen 
are  replaceable  by  metallic  atoms,  which  are  united  to  the  neg- 
ative radical  by  a  vinculum  consisting  of  an  equal  number  of 
oxygen  atoms.  The  hydrogen  and  oxygen  atoms  thus  paired 
are  equivalent  to  so  many  atoms  of  the  radical  hydroxyl  [70]. 
Phosphorous  anhydride  is  the  only  one  of  this  class  of  com- 
pounds in  which  the  phosphorus  atoms  are  not  quinquivalent. 

184.  Phosphoric  Anhydride  is  readily  prepared  by  burning 
phosphorus  in  dry  air.     It  is  an  amorphous  white  powder,  hav- 
ing an  intense  affinity  for  water,  and  is  sometimes  used  as  an 
hygroscopic  agent.      It  hisses  when  dropped  into  water,  and 
gives  a  solution  of 

185.  Metaphosphoric  Acid.  —  This  compound  is  obtained  as 
a  vitreous  solid  (glacial  phosphoric  acid)  by  heating  orthophos- 
phoric acid  to  redness.     Its  solution  coagulates  albumen,  and 
one  molecule  of  the  acid  saturates  only  one  molecule  of  sodic 
hydrate.     By  boiling  the  solution  the  acid  loses  its  power  of 
coagulating  albumen,  and  acquires  greater  capacity  of  satura- 
tion, having  changed  into 

186.  Orthophosphoric  Acid.  —  This  is  much  the  most  im- 
portant of  these  compounds.     It  is  readily  prepared  by  boiling 
phosphorus  in  not  too  strong  nitric  acid,  and  evaporating  the 
liquid  product  to  the  consistency  of  syrup.     The  ordinary  phos- 


254  PHOSPHORUS.  [§  187. 

phates  are  all  salts  of  this  acid,  and  one  molecule  of  acid  is  ca- 
pable of  saturating  three  molecules  of  base.  Many  of  the  phos- 
phates are  thus  constituted,  and  these  are,  theoretically  (38), 
the  neutral  salts  ;  but  evidently  we  may  also  have  for  each  base 
two  acid  salts.  Thus  in  the  case  of  soda  we  have 


ff,Na2=-08-=PO,  H*Na=-  08=-PO  ; 

so  in  the  case  of  lime  we  have 

H2,  Ca2l  06I(PO)2,        ff4,  GalO,l(PO) 


Here,  as  in  many  other  cases,  a  diatomic  metal  serves  to  solder 
together  two  molecules  of  the  acid. 

187.  Common  Sodic  Phosphate,  ff,Na2=03=PO  .  12^0,  is 
by  far  the  most  important  of  the  salts  which  phosphoric  acid 
forms  with  the  bases  previously  studied.  It  is,  moreover,  the 
chief  soluble  salt  of  the  acid,  and  is  much  used  in  the  laboratory 
as  a  reagent.  It  is  also  highly  interesting,  theoretically,  be- 
cause it  illustrates  by  its  reactions  the  relations  we  have  just 
been  considering.  A  solution  of  the  salt  is  neutral  to  test-paper, 
but  when  mixed  with  a  solution  of  argentic  nitrate,  also  per- 
fectly neutral,  we  obtain  a  yellow  precipitate  of  argentic  phos- 
phate, Ag^O^PO,  and  at  the  same  time  the  solution  becomes 
acid.  Heat  now  the  salt  to  120°,  and  it  will  be  found  that  it  loses 
twelve  molecules  of  water  ;  "but  when  the  dried  mass  is  dissolved 
in  water,  and  the  solution  evaporated,  we  obtain  crystals  of  the 
same  form  (rhombic  prisms,  Fig.  45)  and  composition  as  before, 
and  which  give  again  the  same  reaction.  But  heat  the  same 
salt  to  a  red  heat,  and  we  have  a  wholly  different  result.  The 
salt  has  lost  thirteen  molecules  of  water  ;  the  residue  is  less 
soluble  than  before.  On  evaporation  we  obtain  crystals  of  a 
different  form  and  composition  (Na4P207  .  KX/ZjO),  and  the 
solution,  after  precipitation  with  argentic  nitrate,  although  pre- 
viously alkaline,  becomes  neutral.  Moreover,  the  precipitate, 
instead  of  being  yellow,  is  white,  and  has  the  composition 


188.  Microcosmic  Salt.  H,NH*Na=-OfPO  .  ±H20.  —  If  we 
mix  together  hot  saturated  solutions  of  common  sodic  phosphate 
and  sal  ammoniac,  we  obtain  the  following  reaction  :  — 

H20  +  Aq)  = 

.  4ff20  +  (NaCl  +  Aq).  [180] 


§189.]  PHOSPHORUS.  255 

As  the  solution  cools,  the  microcosmic  salt  crystallizes  out,  leav- 
ing sodic  chloride  in  solution.  This  salt,  when  ignited,  loses 
both  its  water  and  its  ammonia,  and  the  sodic  metaphosphate, 
which  remains,  fuses  into  a  colorless  glass  at  a  red  heat.  This 
glass  acts  very  much  like  borax,  and  is  used  in  the  same  way 
as  a  blow-pipe  flux. 

189.  Phosphorus  and  Hydrogen.  —  When  phosphorus  is 
boiled  with  strong  potash  or  soda  lye,  or  with  milk  of  lime,  a 
gas  is  evolved,  called  phosphuretted  hydrogen,  which  on  com- 
ing in  contact  with  the  air  inflames  spontaneously.  This  gas 
consists  almost  entirely  of  the  compound  ff3P  ;  and  when  soda  is 
used,  the  reaction  by  which  it  is  formed  is  as  follows  :  — 

Aq)  = 

[181] 


This  crude  product,  however,  is  not  pure  ff3P  ;  for  when  it  is 
passed  through  a  tube  cooled  by  a  freezing  mixture  it  deposits 
a  small  amount  of  a  very  volatile  yellow  liquid,  which  has  been 
found  to  be  a  second  compound  of  phosphorus  and  hydrogen, 
H±Pft  and  has  the  property  of  inflaming  spontaneously  to  a  high 
degree.  Moreover,  the  gas  thus  treated  loses  its  power  of  self- 
lighting,  and  this  quality  in  the  crude  product  is  evidently  due 
to  a  small  admixture  of  the  liquid  substance.  When  exposed 
to  the  direct  sunlight,  the  liquid  compound  gives  off  HSP,  and 
deposits  a  yellow  solid,  which  is  a  third  compound  of  phospho- 
rus and  hydrogen,  HZP±. 

5ff4P2  =  HJ>±  +  6#3P.  [182] 

This  same  solid  compound  is  deposited  on  the  sides  of  the  ves- 
sel when  the  crude  product  first  mentioned  is  exposed  to  the 
sunlight,  and  in  this  case,  also,  the  gas  loses  its  self-lighting 
power. 

There  are,  then,  three  distinct  compounds  of  hydrogen  and 
phosphorus.  But  of  these  the  first  is  by  far  the  most  impor- 
tant, and  the  other  two  are  chiefly  interesting  as  explaining  the 
singular  phenomena  just  noticed.  The  compound  HZP  is  the 
analogue  of  ammonia  gas,  and  differs  from  it  in  composition  only 
in  containing  in  the  place  of  nitrogen  the  next  lower  element 
of  the  same  chemical  series.  But  the  differences  in  properties 


256  PHOSPHORUS.  [§190. 

are  so  great  that  to  superficial  observation  it  would  seem  as  if 
there  were  no  similarity  between  the  two  compounds.  Thus 
phosphuretted  hydrogen  is  insoluble  in  water,  except  to  a  very 
slight  degree,  and  does  not  unite  with  any  of  the  common  acids. 
A  more  careful  study,  however,  discovers  very  marked  resem- 
blances, for  it  appears  that  H3P  does  unite  with  HBr  and  HI 
to  form  the  compounds  (H±P)Br  and  (H4P)I,  which  resemble 
and  (H4N)I.  Moreover,  the  atoms  of  hydrogen  in 
may  be  replaced  by  methyl,  CH%,  ethyl,  C2H5,  and  other 
radicals  yielding  compounds  similar  to  the  tertiary  amines,  which 
we  call  the  phosphines  ;  and  it  further  appears  that  the  phos- 
phines  have  a  strong  basic  character,  combining  with  all  the 
ordinary  acids  to  form  a  class  of  salts  corresponding  to  those  of 
the  compound  ammonias,  and  yielding  also,  by  reactions  similar 
to  [177]  and  [178],  compounds  analogous  to  the  hydrates  of 
the  ammonium  radicals.  There  are,  however,  even  here,  dif- 
ferences to  be  noted,  —  quite  important,  because  they  point  to  a 
tendency  in  the  series  which  develops  into  a  marked  character 
in  the  next  element,  arsenic.  The  compounds  trimethylphos- 
phine,  (Cff3)3P,  and  triethylphosphine,  (C2ff5)3P,  not  only 
combine  with  acids,  but  they  also  unite  as  diatomic  radicals 
either  with  two  atoms  of  chlorine,  bromine,  or  iodine,  or  with 
one  atom  of  sulphur  or  of  oxygen.  Thus  are  formed  the  crys- 
talline compounds 

(  02ff5)sP-  C12,  (  02ff5)3P-  0,  (  02ff5)3P-S. 

Lastly,  a  compound  has  been  described  corresponding  to  liquid 


phosphuretted  hydrogen,  and  having  the  symbol 
(Cffs)2P,  which,  like  the  former,  is  both  liquid  and  spontane- 
ously inflammable.  It  has,  moreover,  the  properties  of  a  feeble 
basic  radical,  and  in  the  chemical  series  finds  its  analogue  on 
one  side  in  the  radical  amidogen,  and  on  the  other  in  the  re- 
markable compound  kakodyl  (198). 

190.  Phosphorus  and  Chlorine.  —  Phosphorus  combines 
with  chlorine  in  two  proportions.  When  the  phosphorus  is  in 
excess,  phosphorous  chloride,  P073,  is  formed,  which  is  a  fuming, 
colorless  liquid.  When,  on  the  other  hand,  the  chlorine  is  in 
excess,  we  obtain  phosphoric  chloride,  PCI&  a  white  crystalline 
solid.  Both  compounds  are  decomposed  by  water,  and  when 
the  water  is  in  large  excess  the  reactions  are  as  follows  :  — 


§192.]  ARSENIC.  257 

PC/3  +  (3ff20+Aq)  =  (H/0./PffO  +  3IfCl  +  Aq).  [183] 
PC15  +  (±ff20  +  Aq)  =  (H^O^PO  +  5HCl  +  Aq).  [184] 


If  in  the  last  reaction  water  is  not  present  in  sufficient  quantity, 
we  obtain  quite  a  different  result. 


PC15  +  ff20  =  PC130  +  ZffCl.  [185] 

The  first  of  the  three  reactions  is  important,  because  it  gives 
an  easy  method  of  preparing  phosphorous  acid,  and  the  last  has 
a  special  interest  because  it  illustrates  a  valuable  application  of 
phosphoric  chloride.  This  reagent  gives  us  the  means  of  re- 
placing an  atom  of  oxygen  with  two  atoms  of  chlorine,  and  (as 
is  illustrated  not  only  by  [185],  but  also  by  [34])  this  simple 
change  frequently  gives  a  clew  to  the  molecular  constitution  of 
a  chemical  compound.  The  compound  PC130  is  called  phos- 
phoric oxychloride,  and  there  is  also  a  phosphoric  sulphochlo- 
ride,  PC13S.  Both  are  fuming,  colorless  liquids.  The  last, 
when  heated  with  a  solution  of  caustic  soda,  gives  the  following 
remarkable  reaction  :  — 


(PG13S  + 

[186] 


191.  ARSENIC.  As  =  75.  —  Trivalent  or  quinquivalent. 
One  of  the  less  abundant  elements,  but  in  minute  quantities 
quite  widely  distributed.     Found  native,  and  in  combination 
both  with  sulphur  and  with  many  of  the  metals.     The  most 
abundant  of  the  native  compounds  is  Mispickel,  FeS2  .  FeAsr# 
and  by  simply  heating  this  mineral  in  a  closed  vessel  the  ele- 
mentary substance  is  easily  obtained. 

2Fe2As2S2  =  4FeS+Ast.  [187] 

It  is  also  prepared  by  subliming  a  mixture  of  arsenious  anhy- 
dride and  charcoal. 

2As2  03  +  3  O  =  As4  +  3  CO?  [188] 

192.  "Metallic  Arsenic"  As4,  has  a  bright,  steel-gray  lustre, 
and  conducts  electricity  with  readiness.      It  is,  therefore,  fre- 
quently classed  among  the  metals,  and  hence  the  trivial  name. 

Q 


258  ARSENIC.  [§193. 

On  the  other  hand,  it  is  very  brittle,  and  closely  allied  in  all  its 
chemical  relations  to  the  class  of  elements  with  which  it  is  here 
grouped.  Arsenic,  like  phosphorus,  is  dimorphous,  and  may 
readily  be  crystallized  both  in  octahedrons  of  the  first  system, 
and  in  rhombohedrons  of  the  third.  Corresponding  to  these 
two  forms  are  two  allotropic  modifications,  distinguished  also  by 
differences  of  density  and  of  other  physical  qualities,  although 
these  differences  are  not  so  marked  as  those  between  the  two 
states  of  phosphorus.  In  its  ordinary  condition,  arsenic,  when 
heated  out  of  contact  with  the  air,  begins  to  volatilize  at  about 
130°  without  previously  melting,  and  it  cannot  be  brought  into 
the  liquid  condition  except  under  pressure.  The  Sp.  Gr.  of 
the  solid  is  5.75,  and  that  of  the  vapor  referred  to  air  10.6. 
Heated  in  contact  with  the  air,  it  burns  with  a  pale  blue  flame, 
and  the  product  of  the  combustion  is  arsenious  anhydride,  As203. 
It  cannot,  however,  maintain  its  own  combustion,  and  goes  out 
unless  the  temperature  is  kept  above  the  point  of  ignition  by 
external  means.  At  the  ordinary  temperature  it  rapidly  tar- 
nishes in  the  air,  and,  when  in  large  bulk,  the  oxidation  is  some- 
times sufficiently  rapid  to  ignite  the  mass.  Serious  accidents 
have  originated  from  this  cause.  The  burning  of  arsenic  is 
attended  with  a  peculiar  odor  resembling  garlic,  which  is  very 
characteristic.  It  is  insoluble  in  water  or  any  of  the  ordinary 
solvents. 

193.  Arsenic  and  Oxygen.  —  Arsenious  Anhydride.  As203. 
—  The  white  powder  which  is  formed  by  the  burning  of  arsenic 
is  the  most  important  and  the  best  known  of  the  compounds  of 
this  element.  It  is  obtained  in  very  large  quantities  as  a  sec- 
ondary product  in  the  roasting  of  many  metallic  ores.  Like  ar- 
senic itself,  this  compound  is  dimorphous,  and  may  be  obtained 
crystallized  both  in  octahedrons  of  the  first  system  and  in  rhom- 
bic prisms  of  the  fourth.  Moreover,  when  freshly  sublimed,  it 
appears  as  a  vitreous  solid,  and  in  this  third  state  it  is  three 
times  more  soluble  in  water  than  in  the  crystalline  condition. 
Common  white  arsenic  is  only  sparingly  soluble  in  water,  but 
by  continuous  boiling  with  water  this  crystalline  condition  is 
changed  into  the  vitreous  (or  colloidal)  modification,  and  a  much 
larger  amount  enters  into  solution.  This  change,  however,  is 
not  permanent,  and  after  long  standing  the  excess  before  dis- 
solved is  all  deposited  in  octahedral  crystals.  When  digested 


§194.]  ARSENIC.  259 

with  the  mineral  acids,  or  with  aqna  ammonia,  white  arsenic 
dissolves  still  more  readily  than  in  water,  but  on  standing,  the 
larger  part  of  the  As203  is  deposited  from  these  solutions  in  oc- 
tahedral crystals  as  before,  and  by  evaporation  the  whole  may 
be  thus  recovered,  indicating  that  no  stable  compound  had  been 
formed. 

194.  Arsenites.  —  Arsenidus  acid,  ff3=03=As,  is  only  known 
in  solution;  and  indeed  there  is  no  evidence  that  As203  forms 
with  water  a  definite  hydrate.  There  are,  however,  several 
well-defined  arsenites. 


Potassic  Arsenite  (Fowler's  Solution)  H»K=  03=As, 

Cupric  Arsenite  (Scheele's  Green)  JI,Cu=03=As, 

Argentic  Arsenite  (Brilliant  Yellow)  Ag3=O^As. 

The  first  is  obtained  by  adding  to  a  solution  of  caustic  potash 
an  excess  of  As2  03,  and  the  last  two  are  precipitated  when  a 
solution  of  the  first  is  added  to  the  solution  of  a  silver  or  copper 
salt.  Arsenious  anhydride  is  a  most  violent  mineral  poison. 
It  is  also  a  powerful  antiseptic,  and  is  much  used  in  packing 
hides  and  for  preserving  anatomical  preparations. 

195.  Arsenic  Acid,  JT/03=AsO,  is  readily  obtained  by  treat- 
ing As203  with  nitric  acid. 


As2  03  +  2#-  0-N02  +  2ff20  =  2ff3-=03zAs  0  +  N2  03.  [189] 

On  evaporating  the  resulting  solution  under  regulated  condi- 
tions of  temperature,  definite  hydrates,  all  white  solids,  may  be 
obtained  corresponding  to  the  three  conditions  of  phosphoric 
acid.  But  they  differ  from  the  latter  in  that  when  dissolved  in 
water  they  all  yield  solutions  having  the  same  properties  and 
containing  the  same  tribasic  acid.  From  this  acid  a  large  num- 
ber of  arseniates  may  be  prepared.  The  following,,  all  of  which 
may  be  obtained  in  well-defined  crystals,  are  isomorphous  with 
the  corresponding  phosphates  :  — 


.ff20,  H^  03=-As  0. 

These  salts  may  be  all  rendered  anhydrous  by  heat,  and  from 
the  acid  salts  products  may  be  thus  obtained  corresponding  in 


260  ARSENIC.  f§196. 

composition  to  the  meta  and  pyro-phosphates  ;  but  when  dis- 
solved they  reunite  with  water  and  become  tribasic.  Hence 
aqueous  solutions  of  all  these  arseniates  give,  with  argentic  ni- 
trate, the  same  precipitate,  Ag3=0&=AsO.  This  precipitate  has 
a  brick  -red  color,  and  enables  us  to  distinguish  an  arseniate 
from  an  arsenite.  It  is  not  formed,  however,  if  an  excess  of 
ammonia  or  a  free  acid  is  present.  On  adding  a  solution  of 
magnesic  sulphate  containing  an  excess  of  ammonia  to  a  solu- 
tion of  an  arseniate,  a  precipitate  is  obtained,  (H4N),Mg=03= 
AsO  .  6^0,  which  very  closely  resembles  the  corresponding 
precipitate  obtained  with  a  phosphate  under  the  same  conditions. 

196.  Arsenic   Anhydride,  As205,   is   obtained   as   a   white 
amorphous  solid  when  arsenic  acid  is  heated  nearly  to  redness. 
At  a  higher  temperature  it  fuses  and  is  decomposed  into  As203 
and  0=0. 

197.  Arsenic  and  Hydrogen.  —  There  are  two  compounds, 
a  solid,  H±Asz,  and  a  gas,  H3  As.      The  gas  is  formed  whenever 
hydrogen,  in  its  nascent  condition,  comes  in  contact  with  a  com- 
pound of  arsenic,  and  its  formation  gives  us  one  of  the  most 
delicate  means  of  detecting  the  presence  of  arsenic  in  cases  of 
poisoning.     Thus,  when  arsenious  acid  is  introduced  into  an 
apparatus  evolving  hydrogen,  we  have  the  reaction 


ffs=-03=-As  +  SU-ff=  3ff20  +  H3As.         [191] 

As  thus  obtained,  however,  the  gas  is  more  or  less  mixed  with 
hydrogen.  It  may  be  obtained  pure  by  the  following  re- 
action :  — 


Sn3As2  +  (KffCl+  Aq)  =  (3Sn  O12  +  Aq)  +  231^8.  [192] 

It  is  a  colorless  gas  (Sp.  Gr.  33.9),  which  may  be  condensed  to 
a  liquid  boiling  at  30°.  It  has  a  repulsive  odor,  and  is  exceed- 
ingly poisonous.  It  burns  in  the  air,  forming  As203  and  H20. 
In  the  interior  of  the  flame  the  combustion  is  imperfect,  and 
hence  the  flame  deposits  on  a  cold  surface,  which  is  pressed 
upon  it,  a  brilliant  mirror  of  metallic  arsenic.  The  gas  is  de- 
composed when  passed  through  a  red-hot  glass  tube,  and  a  sim- 
ilar mirror  is  formed  on  the  inner  surface  in  front  of  the  heated 
portion.  By  careful  experimenting  these  mirrors  may  be  ob- 
tained with  hydrogen  gas,  which  contains  only  a  mere  trace  of 


§198.]  ARSENIC.  261 

arsenic.  When  arseniuretted  hydrogen  is  passed  into  a  solu- 
tion of  argentic  nitrate,  we  obtain  the  following  remarkable 
reaction :  — 


H3As  +  SAg-O-NO, 

SJf-0-N02  +  ff3=-03-=AsO.  [193] 


198.  Compounds  with  the  Alcohol  Radicals.  —  Arsenic  forms 
compounds  analogous  to  the  amines,  phosphines,  and  their  de- 
rivatives. The  compounds  trimethyl-arsine,  (CH3)3As,  and  tri- 
ethyl-arsine,  (  C2H5)3As,  do  not,  however,  like  the  corresponding 
phosphines,  combine  directly  with  HCl  and  the  similar  acids, 
but  they  do  unite  very  readily  with  two  atoms  of  chlorine,  bro- 
mine, or  iodine,  or  with  one  atom  of  oxygen  or  sulphur,  forming 
such  compounds  as 

(CH^As-Cl^    (C2ff5)BAs=£r2,    (Cff3)3As=0,    (O2H,}3As-S. 

They  also  unite  with  the  iodides  and  bromides  of  the  alcohol 
radicals,  forming  such  compounds  as 

(Cff3)4As-I        or         (CvH^As-Br, 

and  from  these  may  be  derived  basic  compounds  analogous  to 
ammonic  hydrate,  like 

(CH^As-0-H       or        (C2H5),As-0-H. 

But  by  far  the  most  important  of  this  class  of  compounds  are 
those  which  may  be  regarded  as  derived  from  a  remarkable 
radical  substance,  (Cff3)2As-(CH3)2As,  called  kakodyl,  which 
is  formed  when  a  mixture  of  arsenious  anhydride  and  potassic 
acetate  is  submitted  to  distillation  in  a  closed  retort  A  crude 
complex  product  is  thus  obtained,  from  which  the  radical  sub- 
stance may  be  subsequently  separated.  Pure  kakodyl  is  a 
spontaneously  inflammable,  exceedingly  fetid,  fuming  liquid, 
resembling  in  many  respects  the  corresponding  compound  of 
phosphorus.  It  enters  into  direct  combination  with  several  of 
the  elements,  and  is  one  of  the  best  defined  of  the  radical  sub- 
stances. Representing  the  group  of  atoms  (Cff3)2As  by  Kd, 
the  symbols  of  a  few  of  the  more  characteristic  compounds  will 
be  as  follows  :  — 


262  ARSENIC.  [§198. 

Kakodyl  Ed-Ed, 

Kakodylous  Oxide  KdzO, 

Kakodylic  Oxide  Kd20^ 

Kakodylic  Acid  H-  0-KdO, 

Kakodylic  Anhydride  ?  Kd2  0&, 

Kakodylous  Sulphide  Kd^S, 

Kakodylic  Sulphide  Kd& 

Sulpho-kakodylic  Acid  H-S~KdS, 

Sulpho-kakodylic  Anhydride  Kd2S8l 

Kakodylous  Chloride,  Bromide,  or  Iodide  KdCl,KdBr,  or  Kdl, 

Kakodylic  Chloride,  Bromide,  or  Iodide  Kd  Cl3,Kd£r3,  or  Kdl* 

The  mutual  relations  of  the  different  compounds  studied  in 
this  section  are  illustrated  by  the  following  scheme,  which 
includes  all  the  known  compounds  of  arsenic  with  methyl 
(Me  =  Cff3)  and  chlorine  :  — 

Type  H3N.  Type  CtH^N. 


Cl,Me,Me  -As,  Cl,  Cl,Me,Me,Me  ~=As, 

Cl,  Cl,Me^As,  Cl,  Cl,  Cl,Me,MelAs, 

Gl,  Cl,  CteAs,  Cl,Cl,  Cl,  Cl,MelAs. 

By  direct  union  with  C72,  the  compounds  of  the  first  column 
may  be  changed  into  the  compounds  of  the  second  column  on 
the  next  lower  line,  and  the  compounds  of  the  second  column, 
when  heated,  break  up  into  MeCl,  and  the  corresponding  com- 
pound of  the  first  column  on  the  same  line.  Moreover,  the 
first  compound  of  the  first  column  unites  directly  with  MeCl  to 
form  the  first  compound  of  the  second  column.  Besides  the 
compounds  mentioned  above,  this  scheme  includes  another  class 
of  compounds,  which  may  be  regarded  as  formed  from  the  rad- 
ical (Cff^As  (corresponding  to  HN),  not  yet  isolated.  Such 
are 

(Cffs)As=I2,  (Cff3)As=0, 


They  are  called  arsenmonomethyl  iodide,  oxide,  &c.,  and  the 
last,  arsenmonomethylic  acid.  It  is  evident  that  the  atomicity 
of  the  radical  is  not  the  same  in  all  the  compounds. 


§  203.]  ARSENIC.  263 

199.  Compounds  with   Chlorine,  Bromine,  and  Iodine.  — 
These  elements  unite  directly  with  arsenic,  but  only  in  one 
proportion  forming  AsCl&  AsJSrs,  and  AsI3.     The  first  is  a 
liquid,  the  last  two  are  volatile  solids  at  the  ordinary  tempera- 
ture of  the  air.     They  are  all  decomposed  by  water. 

2AsBrs  +  3ff20  =  As2  03  -f  ZHBr.  [194] 

200.  Compounds  with  Sulphur.  —  Arsenic  and  sulphur  may 
be  melted  together  in  all  proportions.     They  also  form  several 
distinct  compounds.     The  most  important  are 

201.  Realgar,  As2S2l  a  brilliant  red  solid,  much  used  as  a 
pigment,  and  found  in  nature  well  crystallized. 

202.  Orpiment,  As2S3,  a  brilliant  yellow  solid,  also  used  as  a 
paint.     Formed  whenever  arsenic  is  precipitated  from  its  solu- 
tions by  H2S.     Also  found  crystallized  in  nature.     Soluble  in 
ammonia  and  caustic  alkalies,  and  precipitated  from  such  solu- 
tions by  acids. 

203.  Arsenic  Sulphide.  As2S5.  —  Only  known  in  combination. 
The  last  two  compounds  are  "  sulphur  anhydrides,"  and  form 

with  the  sulphur  bases  a  very  large  and  important  class  of  sul- 
phur salts,  many  of  which  are  native  compounds  and  important 
metallic  ores.  The  following  reactions  will  illustrate  the  forma- 
tion of  compounds  of  this  class  :  — 

As2S3  +  (1K-0-H+  Aq)  = 

fAs  +  H20  +  Aq),  [195] 


(ff,Na2-=S3=-As  +  3ff20  +  Aq).  [196] 

Sulpho-arsenites. 

Proustite,  Hexagonal  Ag^S^As, 

Tennantite,  Isometric  [Cu^lS^lAs^  .  FeS, 

Sartorite,  Orthorhombic  Pb=S2=AszS^ 

Dufrenoysite,  Orthorhombic 

Sulpho-arsem'ates. 
Enargite,  Orthorhombic 


264  ANTIMONY.  [§204. 

These  symbols  should  be  compared  with  those  of  the  corre- 
sponding compounds  of  antimony,  in  connection  with  which 
their  mutual  relations  will  be  explained. 

204.  Characteristic  Reactions.  —  The  importance  of  proving 
the  presence  or  absence  of  arsenic  in  cases  of  suspected  poison- 
ing has  led  to  a  most  careful  study  of  the  characteristic  reac- 
tions of  this  element,  and  hence  our  knowledge  on  these  points 
is  unusually  accurate  and  full.     The  most  striking  of  these  re- 
actions have  already  been  given.     Further  details  or  descrip- 
tions of  methods  by  which  arsenic,  even  when  in  minute  quan- 
tities, may  be  detected  and  distinguished  from  antimony  lie 
beyond  the  scope  of  the  present  work. 

205.  ANTIMONY.  Sb  =  122.  —  Trivalent  or  quinquiva- 
lent.    This  element  is  less  abundantly  distributed  than  arsenic, 
although  found  in  similar  associations.     The  most  abundant  na- 
tive compound  is  the  gray  sulphide  (Antimony  Glance),  Sb.2S3, 
which  occurs  not  only  in  a  pure  state,  but  also  in  combination 
with  other  metallic  sulphides.    Antimony  is  sometimes,  although 
rarely,  found  in  the  metallic  state,  and  likewise  in  combination 
with  oxygen. 

206.  Metallic  Antimony,  Sb?,  is  most  readily  extracted  from 
the  native  sulphide  by  smelting  the  ore  with  metallic  iron. 

Sb2S3  -f  3Fe  =  3FeS  +  Sb*  [197] 

It  is  also  extracted  by  first  roasting  the  ore, 

2Sb.2S3  +  90=0  =  2Sb203  -f  QS021  [198] 

and  then  melting  with  charcoal  and  sodic  carbonate.  The  last 
converts  into  oxide  the  small  portion  of  the  sulphide  which  es- 
caped oxidation  in  the  roasting  process, 


fOO  =  Sb203  +  3Na2S  +  3  C02,  [199] 
and  the  charcoal  reduces  the  oxide  to  metallic  antimony, 

Sb203  +  30  =  Sb,  +  3  00.  [200] 

By  oxidizing  the  crude  metal  with  nitric  acid,  and  again  re- 
ducing with  charcoal,  the  antimony  may  be  obtained  in  a 
pure  condition. 


§206.]  ANTIMONY.  265 

Antimony  is  closely  allied  to  arsenic,  but  possesses  the  prop- 
erties of  a  metal  to  a  still  higher  degree.  It  has  a  bright  me- 
tallic lustre,  which  it  preserves  in  the  air.  It  has  a  high  Sp. 
Gr.  (6.7),  and  conducts  heat  and  electricity  with  facility.  Its 
conducting  power,  however,  is  inferior  to  that  of  the  perfect 
metals,  and,  moreover,  it  is  very  brittle  and  may  be  readily  re- 
duced to  powder.  It  has  also  a  highly  crystalline  structure, 
and  like  arsenic  it  may  be  obtained  crystallized  both  in  rhom- 
bohedrons  of  the  third  system,  and  in  octahedrons  of  the  first. 
The  first  is  the  common  form,  and  lumps  of  the  metal  may  some- 
times be  cleaved  parallel  to  the  rhombohedral  planes,  which  are 
always  more  or  less  evident  on  the  fractured  surface.  Antimony 
melts  at  430°,  and  it  volatilizes,  but  only  very  slowly,  at  a  full 
red  heat.  The  melted  metal,  when  heated  in  the  air,  slowly  ox- 
idizes, and  before  the  blow-pipe  it  burns,  the  product  of  the 
oxidation  being  in  either  case  Sb203.  Antimony  is  only  very 
slightly  acted  on  by  pure  hydrochloric  acid,  even  when  concen- 
trated and  boiling  ;  but  on  the  addition  of  a  very  small  amount 
of  nitric  acid  the  metal  dissolves  easily,  forming  a  solution  of 


Sb2  +  (GHCl  +  6HN03  +  Aq}  = 

(2SbCl3  +  QIf20  +  Aq)  -f  6N02.  [201] 

With  the  aid  of  heat  it  dissolves  in  strong  sulphuric  acid. 
Sb2  +  Sff2S04  =  Sb2W6l(S02)3  +  3S02  +  QH20.  [202] 


Nitric  acid,  when  in  excess,  converts  the  metal  into  a  white 
powder  insoluble  in  the  acid  (chiefly  Sb204).  If,  however,  the 
nitric  acid  contains  a  little  hydrochloric  acid,  the  product  is 
metantimonic  acid. 


2H-0-Sb02  +  H20  +  N203  +  2NO.  [203] 

Lastly,  antimony  dissolves  readily  in  a  mixture  of  tartaric 
and  nitric  acids,  which  is  one  of  the  best  solvents  of  the  metal. 
Metallic  antimony  is  chiefly  used  in  the  arts  to  alloy  with  other 
metals,  to  which  it  imparts  a  greater  hardness  and  durability. 
Type-metal  is  an  alloy  of  four  parts  of  lead  and  one  of  antimony. 
This  alloy  expands  in  "  setting,"  and  therefore  takes  a  sharp 
12 


266  ANTIMONY.  [§207. 

impression  of  the  mould  in  which  it  is  cast  ;  and  this  property, 
as  well  as  the  hardness,  renders  type-metal  peculiarly  suitable 
to  the  important  use  to  which  it  is  applied.  Britannia  metal, 
an  alloy  of  brass,  antimony,  tin,  and  lead,  much  used  as  the  base 
of  plated  silver-ware,  also  owes  its  hardness  and  durability  to 
the  antimony  it  contains. 

207.  Antimony  and  Chlorine.  —  Antimonious  Chloride. 
SbCl3.  —  A  solution  of  this  compound  is  readily  obtained  either 
by  [201]  or  by  dissolving  the  native  sulphide  in  hydrochloric 
acid.  On  evaporating  the  excess  of  acid,  and  distilling  the  resi- 
due, the  chloride  is  obtained  as  a  white  crystalline  solid.  It  is 
deliquescent,  very  volatile,  and  melts  so  readily  (72°)  that  it 
was  formerly  known  as  butter  of  antimony.  The  Sp.  Gr.  of 
its  vapor,  as  found  by  experiment,  is  1  12.7.  Antimonious  chlo- 
ride may  also  be  obtained  by  distilling  antimony  or  antimonious 
sulphide  with  mercuric  chloride,  and  al^o  by  distilling  a  mixture 
of  antimonious  sulphate  wiih  common  salt. 


[204] 

Sb2S3  +  Sffg  C12  =  3HgS  +  2  ^bOl3.  [205] 

=  3Na2=02=S02  +  2SbCl3.  [206] 


Antimonious  chloride  is  decomposed  by  water,  forming  an 
insoluble  oxychloride  and  hydrochloric  acid.  Hence  the  solu- 
tion obtained  by  [201]  becomes  turbid  when  diluted  with  water. 
The  presence  of  tartaric  acid  in  sufficient  quantity  prevents  the 
decomposition,  and  a  solution  of  this  acid  dissolves  the  oxychlo- 
ride when  formed.  By  long-continued  washing  the  oxychloride 
may  be  converted  into  antimonious  oxide. 

(SbCl,  +  ff20  +  Aq)  =  SbOCl  +  (2HCI  +  Aq).  [207] 
2SbOCl+  (H20  +  Aq)  =  &k203  +  (2ffCl  +  Aq).  [208] 


Antimonious  chloride  combines  with  the  chlorides  of  the 
metals  of  the  alkalies  and  of  the  alkaline  earths,  and  forms  sol- 
uble crystalline  salts.  Hence  it  may  be  mixed  with  concen- 
trated solutions  of  these  chlorides,  as  also  with  strong  hydro- 
chloric acid,  without  undergoing  decomposition.  The  following 
are  the  symbols  of  a  few  of  these  double  chlorides,  which  are 
best  regarded  as  molecular  compounds  :  — 


§209.]  ANTIMONY.  267 


•  1  JJ210,1 
3KCl.SbCl3,  2KCl.SbCl9, 

.  SbCl3. 


208.  Antimonic  Chloride,  Sb  Cl&  may  be  formed  by  passing 
chlorine  gas  over  Sb  C13,  or  by  acting  on  the  metal  with  an  ex- 
cess of  the  same  reagent.  It  is  a  volatile,  fuming  liquid,  which 
readily  parts  with  two  fifths  of  its  chlorine,  and  is  therefore 
sometimes  used,  like  PC15,  as  a  chloridizing  agent.  It  is  at 
once  decomposed  by  water.  With  only  a  small  quantity  it  forms 
an  oxychloride  (compare  [185]). 

ff2  o  +  Sb  C15  =  2HCI  +  Sb  C13  0.  [209] 

With  an  excess  of  water,  either  ortho-antimonic  acid  or  pyro- 
antimonic  acid  results. 


SbCls  +  4#20  =  HfOfSbO  +  5HCI,        [210] 
or  2SbCl5  +  7ff20  =  H4W^Sb20B  +  WHCL     [211] 


The  presence  of  tartaric  acid  prevents  these  reactions.  By 
the  action  of  H2S  on  Sb  C15  a  sulpho-chloride  may  be  formed. 

Sb  C15  +  H2S  =  Sb  C13S  +  2HCL  [212] 

A  bromide  of  antimony,  SbBr3,  and  an  iodide,  Sbl&  are 
readily  formed  by  the  direct  action  of  these  elements  on  the 
metal,  but  no  penta-bromide  or  iodide  has  yet  been  obtained. 
They  are  both  fusible  and  volatile  solids,  and  when  acted  on  by 
water  are  converted  into  SbBrO  and  SblO.  The  correspond- 
ing fluoride  dissolves  in  water  without  decomposition,  and  forms 
with  the  alkaline  fluorides  a  number  of  double  salts. 


ZNaF.  SbF3,  2(ff4N)F.  SbF^  KF  .  SbF3. 

209.  Antimony  and  Oxygen.  —  Antimonious  Oxide.  Sh203. 
—  This  compound,  already  mentioned  as  a  product  of  the  direct 
oxidation  of  antimony,  may,  like  As20&  be  obtained  crystallized 
both  in  octahedrons  of  the  first  system  or  in  rhombic  prisms  of 
the  fourth,  and  on  this  difference  of  form  depends  the  distinc- 

1  These  symbols  are  thus  written  to  show  the  relations  of  the  compounds. 
To  be  strictly  accurate  they  should  be  doubled. 


268  ANTIMONY.  [§209. 

tion  between  the  two  minerals  Senarmontite  and  Valentinite, 
both  of  which  consist  of  this  same  substance.  The  oxide  is 
most  readily  prepared  artificially  by  pouring  a  solution  of  Sb  C13 
[201]  into  a  boiling  solution  of  sodic  carbonate. 

fCO  +  2SbCls  +  Aq)  = 

Sfo2O3  +  (ZNaCl  +  Aq)  +  3®©*  [213] 


Antimonious  oxide  acts  both  as  a  basic  and  as  an  acid  anhy- 
dride, although  the  first  is  by  far  its  most  marked  character. 
It  is  but  very  slightly  soluble  in  water.  When  the  solution  of 
SbCl3-is  poured  into  a  cold  solution  of  sodic  carbonate,  we 
have  the  reaction, 

(BNofOfCO  +  2SbCl3  +  H20  +  Aq)  = 

2H  O  fcfoO  +  (QNaCl  +  Aq)  +  3®©2,  [214] 

and  the  product  may  be  regarded  as  metantimonious  acid,  for 
it  dissolves  in  caustic  alkalies  and  forms  definite,  although  very 
unstable,  salts.  On  the  other  hand,  the  oxide  dissolves  in  fum- 
ing sulphuric  and  fuming  nitric,  as  well  as  in  hydrochloric  acids, 
forming  crystalline  salts,  in  which  the  antimony  plays  the  part 
of  a  basic  radical. 

The  most  important  salt  of  this  class  is  that  formed  by  dis- 
solving Sb203  in  a  solution  of  acid  potassic  tartrate  (cream  of 
tartar).  This  compound  is  very  much  used  in  medicine  as  an 
emetic,  and  hence  the  trivial  name  tartar  emetic.  Tartaric  acid 
is  tetratomic,  but  only  bibasic  (43),  and  we  have  the  following 
series  of  compounds  :  — 

Tartaric  Acid  H2  ,  Hf  04i(  C4ff2  <92), 

Neutral  Potassic  Tartrate  K2  ,  HfOf(  C4ff202), 

Acid  Potassic  Tartrate  K,H,  H2=0^(  O4H2  6>2), 

Tartar  Emetic  (crystallized)      K,SIO  , 
"  after  heating  to  200° 


It  will  be  noticed  that  in  forming  tartar  emetic  the  radical 
SbO  of  the  compound  ff-O-SbO  takes  the  place  of  one  atom 
of  basic  hydrogen,  which  still  remains  unreplaced  in  cream  of 
tartar.  On  heating  the  crystallized  salt  to  100°  it  gives  up  its 


§210.]  ANTIMONY.  269 

water  of  crystallization.  At  200°  it  gives  off  an  additional 
atom  of  water,  formed  at  the  expense  of  the  oxygen  in  the  rad- 
ical just  named  and  of  the  two  atoms  of  hydrogen  distinguished 
as  negative  in  the  acid;  and  it  will  be  seen  that,  in  the  anhydrous 
salt  thus  obtained,  one  atom  of  antimony  takes  the  place  of  three 
typical  atoms  of  hydrogen  in  tartaric  acid.  Compounds  similar 
to  tartar  emetic  may  be  made  in  a  similar  way  with  the  oxides 
of  arsenic,  bismuth,  and  uranium.  Their  symbols  differ  from 
that  of  tartar  emetic  only  in  having  the  radicals  As  0,  As  02, 
BiO,  or  UO,  in  place  of  SbO,  and  they  undergo  a  similar  de- 
composition when  heated.  Compounds  of  the  same  class  may 
also  be  obtained  with  other  anhydrides  than  those  of  the  group 
of  elements  we  are  now  studying  (as  Fe^0z  Cr20B,  B203,  &c.), 
and  when  it  is  further  added  that  the  potassium  in  these  com- 
pounds may  be  replaced  by  other  univalent  radicals,  or  even  by 
bivalent  radicals  soldering  together  two  molecules  of  the  ordi- 
nary type,  it  will  be  seen  that  a  very  large  number  of  such 
salts  are  possible.  Lastly,  the  fact  that  a  compound  has  been 
prepared  in  which  two  of  the  typical  atoms  of  hydrogen  are 
replaced  by  the  positive  radical  ethyl,  while  the  other  two  are 
replaced  by  the  negative  radical  acetyl,  and  the  additional  fact 
that  no  salt  can  be  obtained  in  which  all  the  four  atoms  are  re- 
placed by  a  well-defined  positive  radical,  give  a  strong  presump- 
tion in  favor  of  the  formula  of  the  tartrates  adopted  above. 

Antimonious  oxide,  when  heated  out  of  contact  with  the  air, 
volatilizes  unchanged,  but  under  the  same  conditions  in  the  air  it 
burns  like  tinder,  forming  a  higher  oxide,  Sb204,  which  is  fixed, 
even  at  a  high  red  heat.  By  ignition  with  charcoal  or  hydrogen, 
all  the  oxides  are  readily  reduced  to  the  metallic  state. 

210.  Antimonic  Acid.  —  The  reactions  l^,ve  already  been 
given  [203],  [210],  [211]  by  which  the  three  conditions  of  this 
acid  may  be  prepared.  They  are 

Metantimonic  Acid  H-  0~Sb  0* 

Orthoantimonic  Acid  ffs=03=SbO, 

Pyroantimonic  Acid 


Pyroantimonic  acid  may  also  be  prepared  by  acidifying  the 
solution  of  acid  potassic  pyroantimoniate  mentioned  below, 

Aq)  = 

SbtOt  +  (2KCI  +  Aq),  [215] 


270  ANTIMONY.  [§211. 

but  when  this  precipitate  is  dried,  it  loses  water  and  changes 
into  metantimonic  acid, 

HfOfSbtOi  —  2ff-0-Sb02  +  HZ0.  [216] 

The  existence  of  orthoantimonic  acid  has  not  been  as  yet 
well  established,  but  the  other  two  are  well  known,  and  many 
of  their  salts  have  been  investigated.  The  most  interesting  of 
these  salts  is  obtained  by  fusing  antimonic  anhydride  with  an 
excess  of  potassic  hydrate,  and  extracting  the  fused  mass  with 
water.  An  alkaline  solution  is  obtained,  containing  a  salt 
whose  composition  is  expressed  by  the  symbol  H^K^O^ =Sb2 03. 
Thi$  solution  produces  a  precipitate  in  solutions  of  salts  of  so- 
dium, and  is  sometimes  used  as  a  reagent  in  testing  for  this 
element.  The  sodic  salt  thus  precipitated  has  the  composition 
HvNa<fOfSb2Oz .  Qff20.  Antimonic  acid,  in  either  of  its  con- 
ditions, is  insoluble  in  water,  as  well  as  the  antimoniates,  with 
a  few  exceptions.  In  this  respect  they  frequently  differ  from 
the  corresponding  compounds  of  phosphorus  and  arsenic,  which 
they  closely  resemble  in  molecular  constitution. 

211.  Antimonic  Anhydride,  Sb205,  is  readily  prepared  by 
gently  heating  metantimonic  acid,  the  product  of  reaction  [203]. 
It  is  a  pale  yellow  powder,  insoluble  in  water.     Fused  with  al- 
kaline hydrates  or  carbonates  it  yields  various  antimoniates. 
When  ignited  alone  it  gives  off  one  fifth  of  its  oxygen,  and  the 
product  is  the  same  white  powder,  Sb^O^  which  is  formed  by 
the  oxidation  of  antimonious  oxide.     This  intermediate  oxide 
is  the  most  stable  of  the  oxides  of  antimony.     It  is  sometimes 
called  antimonious  acid,  and  when  fused  with  the  alkalies  it 
enters  into  combination  with  them,  but  the  products  thus  ob- 
tained may  be  regarded  as  mixtures  of  an  antimonite  and  an 
antimoniate,  and  the  oxide  itself  appears  to  be  an  antimoniate 
of  antimony,  SbO~0-Sb02.     A  rare  mineral  called  Cervantite 
has  the  same  composition. 

212.  A ntimony  and  Hydrogen. — Antimoniuretted  Hydrogen. 
ff3Sb.  —  When  any  soluble  compound  of  antimony  is  added  to 
an  apparatus   evolving  hydrogen   [64],   we  obtain  a  product 
closely  resembling  arseniuretted  hydrogen,  but  containing  anti- 
mony instead  of  arsenic. 

SHGl.  [217] 


§213.]  ANTIMPNY.  271 

The  antimony  compound  thus  formed  is  always  mixed  with 
much  hydrogen  gas,  and  has  not  yet  been  obtained  in  a  pure 
condition.  When  burnt  in  air  it  yields  water  and  antimonious 
oxide. 

2ff3Sb  +  3(9=0  =  Sb203  +  3/7,0.  [218] 

If  burnt  against  a  cold  surface,  so  that  the  combustion  is  incom- 
plete, the  antimony  is  deposited  and  a  metallic  mirror  is  formed. 

4ff8Sb  +  30=0=  Sb4  +  6J3J0.  [219] 

The  compound  is  decomposed  and  a  similar  mirror  formed 
when  the  gas  is  passed  through  a  red-hot  tube. 

When  the  gas  is  transmitted  through  a  solution  of  argentic 
nitrate  we  get  the  reaction 

(3Aff'0-NOi  +  Aq)  +  ffBSb  = 

AgsSb  +  (Sff-0-N02  +  Aq).  [220] 

This  reaction,  and  the  well-established  trivalent  character  of 
antimony,  fix  the  composition  of  antimoniuretted  hydrogen  be- 
yond all  reasonable  doubt. 

Compounds  of  antimony  with  the  alcohol  radicals  have  been 
prepared,  both  after  the  type  of  ammonia  and  that  of  the  am- 
monium salts.  Thus  we  have 

Trimethyl-stibine  (Cff3)3Sb, 

Trimethyl-stibine  Chloride  (CH^SbCH* 

Trimethyl-stibine  Oxide  (Cff3)3SbO, 

Tetramethyl-stibonium  Iodide  (  CH^)±SbI, 

Tetramethyl-stibonium  Hydrate  (Cffs)4Sb-0-ff, 

and  the  corresponding  compounds  of  ethyl  and  amyl.  The  re- 
action of  triethyl-stibine  on  hydrochloric  acid  is  interesting,  as 
it  illustrates  the  serial  relations  among  the  group  of  elements 
we  are  studying.  (C2ff5)3Sb  not  only  does  not  combine  with 
HCl,  but  actually  decomposes  the  acid,  yielding  (C.2ff5)3SbCl2 
and  H-H.  Compounds  of  antimony  corresponding  to  those  of 
the  kakodyl  group  are  not  known. 

213.  Antimony  and  Zinc.  — There  are  two  very  well  marked 
crystalline  compounds  of  antimony  and  zinc,  Zn3Sb2  and  Zn2Sb2, 
which  give  still  further  evidence  of  the  usual  trivalent  charac- 


272  ANTIMONY.  [§214. 

ter  of  antimony.  The  compound  Zn3Sb2,  moreover,  decomposes 
water  with  the  evolution  of  hydrogen  gas. 

214.  Antimony  and  Sulphur  (Crude  Antimony).  —  Anti- 
monious Sulphide.  Sb2S3.  —  The  gray  sulphide  of  antimony  has 
already  been  noticed  as  a  native  product.  It  is  known  to  min- 
eralogists as  Antimony  Glance,  and  is  distinguished  by  its  great 
fusibility.  Large  splinters  of  the  mineral  readily  melt  in  a 
candle  flame.  Hence  it  is  easily  separated  by  fusion  from  the 
gangue  with  which  it  is  found  associated,  and  the  process  is 
termed  "  liquation."  Its  crystals  have  a  bright  metallic  lustre, 
and  the  form  of  rhombic  prisms  of  the  fourth  system  ;  but  a 
strong  tendency  to  longitudinal  cleavage  gives  to  them  a  bladed 
appearance. 

When  antimony  and  sulphur,  or  antimonious  oxide  and  sul- 
phur, are  melted  together  in  proper  proportions,  a  compound  is 
obtained  similar  to  the  native  sulphide.  Moreover,  a  precipi- 
tate of  the  same  composition  falls  when  H2S  is  passed  through 
the  solution  of  any  antimonious  compound.  This  precipitate, 
however,  has  a  brick  red  color,  and  is  probably  an  isomeric 
modification  of  the  native  gray  compound.  It  is  insoluble  in 
dilute  hydrochloric  acid  when  cold,  but  readily  dissolves  in  the 
hot  acid  if  moderately  concentrated.  It  is  also  soluble  in  solu- 
tions of  alkaline  hydrates. 

Sb2S3  +  (QK-0-H+  Aq)  = 

(K3~=S3-=Sb  +  KfOfSb  +  3ff20  +  Aq).  [221] 

From  this  solution  it  is  again  precipitated  on  the  addition  of  an 
acid. 


Aq)  = 
Sb2S3  +  (SKCl  +  3ff20  +  Aq).  [222] 

In  like  manner  it  dissolves  in  solutions  of  alkaline  sulpho- 
hydrates. 

Sb2S3  +  (GK-S-H+  Aq)  — 

b  +  Aq)  +  3ff2S.  [223] 


Antimonious  sulphide  is  a  strong  sulpho-anhydride,  and 
many  of  its  salts  are  important  minerals.  The  following  are  a 
few  examples.  We  give  the  symbols  in  their  simplest  form, 


§214.]  ANTIMONY.  273 

but  in  the  minerals  themselves  the  antimony  is  frequently  more 
or  less  replaced  by  arsenic,  and  the  principal  metallic  radical 
by  others  isoraorphous  with  it.  These  compounds  are  best 
classified  by  referring  them  to  a  series  of  assumed  sulphur  acids, 
related  to  each  other  like  the  successive  anhydrides  of  the  oxy- 
gen acids  (181),  but  derived  from  the  normal  compound  of  the 
series  by  eliminating  successive  molecules  of  H2S.  They  may 
be  distinguished  as  ortho,  meta,  and  pyro-sulphantimonites,  but 
these  terms  have  no  special  appropriateness  except  so  far  as 
they  imply  a  distinction  analogous  to  that  which  obtains  be- 
tween similar  oxygen  compounds. 

• 
Ortho-sulphantimonites. 

Pyrargyrite  Hexagonal  Ag^S^Sb, 

Stephanite  Orthorhombic  A</3=S3=Sb  .  Ag2S, 

Polybasite  Orthorhombic  Ag3=S3=Sb  .  3Ag2S, 

Bournonite  Orthorhombic  [  Cu2'],Pb2  lS6iSb2J 

Meneghinite  Monoclinic  ?  Pb3lS6iSb2  .  PbS, 

Tetrahedrite  Isometric  Cii^  .  ZnS. 


Meta-sulphantimonites. 

Miargyrite  Monoclinic  Ag-S-SbS, 

Zinkenite  Orthorhombic  Pb=SfSb2Sat 

Chalcostibite  Orthorhombic  Cu  -SfSb^ 

Berthierite  Fe=S2=Sb2S2. 

Pyro-sulphantimonites. 

Jamesonite  (feather  ore)          Orthorhombic  Pb2=S^Sb2S, 

Freieslebenite      Monoclinic 


A  few  points  in  connection  with  the  above  formula  require 
further  explanation.  Of  the  three  dyad  atoms  which  compose- 
the  basic  radical  of  the  mineral  Bournonite,  two  are  atoms  of 
lead,  and  one  a  double  atom  (34)  of  copper.  Now  we  may  either 
suppose  that  each  molecule  of  the  mineral  is  constituted  as  our 
symbol  would  indicate,  or  we  may  regard  it  as  a  molecular 
aggregate  of  two  distinct  compounds,  namely,  [  Cu^S^Sby 
and  Pbg=S^iSb^  and  as  containing  for  every  two.  molecules 
12*  R 


274  ANTIMONY.  [§214. 

of  the  last  one  molecule  of  the  first.  In  Freieslebenite,  how- 
ever, the  proportions  of  silver  and  lead  are  such  that  the  com- 
position of  the  mineral  can  only  be  accurately  expressed  in  the 
second  of  the  two  ways  just  indicated,  and  this  is  the  general 
rule  in  the  mineral  kingdom.  Again,  the  minerals  Stephanite, 
Polybasite,  Meneghinite,  and  Tetrahedrite  may  be  best  regarded 
as  molecular  aggregates  of  an  ortho-sulphantimonite  and  a  sim- 
ple. metallic  sulphide,  in  which  the  last  plays  very  much*  the 
same  part  as  the  water  of  crystallization  in  our  ordinary  salts. 
In  all  the  above  cases  the  results  of  analysis  would  indicate 
a  great  constancy  in  the  relative  number  of  heterogeneous  mole- 
cules which  enter  into  the  composition  of  the  mineral  ;  but  in 
other  cases  no  such  constancy  is  observed,  and  one  element  is 
found  replacing  another  in  almost  any  proportion.  In  tetra- 
hedrite,  for  example,  we  frequently  find  the  copper  more  or  less 
replaced  by  silver  or  mercury,  the  antimony  in  like  manner  re- 
placed by  arsenic  or  bismuth,  and  the  zinc  by  iron.  This  we 
express  by  writing  the  symbols  of  the  replacing  elements  to- 
gether within  the  same  brackets.  Thus  [_\_Cu^Ag2,Hg~\  stands 
for  only  one  atom,  but  indicates  that  in  the  mineral  the  copper 
is  more  or  less  replaced  by  silver  and  mercury.  So  also  the 
symbol  \_Zn,Fe~\  represents  only  one  atom,  but  indicates  that 
the  zinc  is  to  a  certain  extent  replaced  by  iron.  In  its  most 
general  form  the  symbol  of  tetrahedrite  would  be  written,  — 


This  symbol  indicates  nothing  in  regard  to  the  relative  propor- 
tions of  the  elements  enclosed  in  the  same  brackets,  and  in  fact 
this  proportion  is  variable  in  different  specimens  of  the  same 
mineral,  but  it  does  show  that,  so  far  as  the  number  of  atoms  is 
concerned,  [[  Cu^Ag^Hg}  :  [SM*,#i]  :  [Zn,Fe~\  =  3:2:1. 

It  is,  of  course,  impossible,  according  to  our  present  theories, 
that  each  molecule  should  have  this  complex  constitution  ;  but 
we  may  suppose  that  in  the  mineral  there  are  certain  molecules 
containing  one  set  of  elements,  and  other  molecules  a  different 
set,  the  actual  specimen  being  an  aggregate  of  all  ;  and  further, 
we  must  suppose  that  there  are  two  kinds  of  molecular  aggre- 
gation, one  in  which  the  molecules  are  united  in  more  or  less 
definite  proportions,  and  a  second  where  they  are  merely  mixed 
in  any  proportions  which  accident  may  have  determined. 


§217.J  BISMUTH.  275 

215.  Antimonic  Sulphide.  Sb2S5.  —  When  ff2S  is  passed 
through  a  solution  of  SbCl^  an  orange-colored  precipitate  is 
formed,  having  the  composition  which  our  symbol  indicates. 
It  may  be  questioned,  however,  whether  the  precipitate  is  not 
an  intimate  mixture  of  Sb2S3  and  S=S,  for  when  treated  with 
sulphide  of  carbon  two  fifths  of  the  sulphur  is  dissolved,  Sb2S3 
being  left  ;  and,  moreover,  it  is  decomposed  by  boiling  hydro- 
chloric acid  into  Sb  Cl&  H2S,  and  S=S.  On  the  other  hand,  it  is 
dissolved  in  alkaline  hydrates  and  sulphides,  forming  sulphanti- 
moniates,  and  from  these  solutions  the  same  substance  is  again 
precipitated  on  the  addition  of  an  acid. 

4Sb2S5  +  (24K-0-H+  Aq)  = 

Aq).  [224] 

Aq).  [225] 

GffCl  +  Aq)  = 

Sb2S5  +  (SKCl  +  Aq)  +  3ff2S.  [226] 


216.  Characteristic  Reactions.  —  The  formation  of  the  red 
sulphide  by  the  action  of  ff2S  is  one  of  the  most  characteristic 
indications  of  the  presence  of  antimony  ;  but,  before  this  test 
can  be  applied,  the  antimony  must  be  separated  from  all  those 
elements  which  would  obscure  the  reaction,  by  the  well-known 
methods  of  qualitative  analysis.     The  blow-pipe  reactions  of 
antimony  are  also  very  characteristic.     They  consist  in  the  for- 
mation of  a  brittle  metallic  bead  or  a  coating  of  volatile  oxide 
on  charcoal,  and  in  the  peculiar  bluish-green  color  which  this 
oxide  imparts  to  the  blow-pipe  flame. 

217.  BISMUTH.  Bi  =  2  1  0.  —  Trivalent  and  quinquivalent. 
One  of  the  rarer  elements.     Usually  found  native,  sometimes 
combined  with  sulphur,  in  bismuth  glance,  J3i2*Ssi  and  rarely 
with  both  sulphur  and  tellurium,  in  tetradymite,  Bi2  Te2S.    Me- 
tallic bismuth  is  readily  extracted  from  the  native  mineral  by 
fusion  (liquation).     After  the  analogy  of  phosphorus  and  ar- 
senic, we  assign  to  the  elementary  substance  the  molecular  for- 
mula Bi±  ;  but  since  the  metal  does  not  volatilize  except  at  a 
very  high  temperature,  we  have  not  been  able  to  determine  its 
molecular  weight  experimentally.     Bismuth  melts  at  265°,  and 
forms  alloys  which  are  remarkable  for  their  great  fusibility. 


276  BISMUTH.  [§218. 

An  alloy  containing  two  parts  of  bismuth,  one  of  lead,  and  one 
of  tin,  melts  at  about  94°,  and  the  addition  of  cadmium  reduces 
the  melting-point  still  lower.  These  alloys  expand  on  hard- 
ening, and  are,  therefore,  useful  for  making  casts. 

As  we  descend  in  the  series  from  antimony  to  bismuth,  the 
metallic  qualities  become  still  more  marked.  The  Sp.  Gr.  of 
bismuth  equals  9.83.  Its  lustre  is  brilliant,  with  a  reddish 
tinge.  It  is  less  brittle  than  antimony,  and  even  is  slightly 
malleable.  Bismuth  may  readily  be  crystallized  in  rhombohe- 
drons  isomorphous  with  those  of  antimony ;  but  it  has  not  yet 
been  crystallized  in  forms  of  the  isometric  system.  Bismuth  is 
not  dissolved  by  strong  hydrochloric  acid,  nor  even  by  sulphuric 
acid,  except  when  concentrated  and  boiling.  Nitric  acid  read- 
ily dissolves  it  with  evolution  of  NO&  forming  a  well-crystal- 
lized nitrate  (distinction  from  antimony).  The  metal  also  dis- 
solves in  aqua-regia,  and  combines  directly  with  chlorine,  bro- 
mine, and  iodine. 

218.  Bismuth  and  the  Alcohol  Radicals.  —  No  compound  of 
bismuth  and  hydrogen  is  known,  but  bismuth  combines  with 
ethyl,  forming  a  very  unstable  liquid,  which  inflames  spontane- 
ously in  the  air  and  explodes  at  150°.     It  has  the  composition 
(  C2ff5)3Bi,  and  from  it  may  be  obtained  the  compound  (  O2ffs)s 
BUz  in  yellow  six-sided  crystalline  plates.     This  is  the  iodide 
of  a  bivalent  radical,  which  forms  also  definite  but  very  unsta- 
ble compounds  with  chlorine  and  oxygen,  and  is  capable  of 
replacing  the  hydrogen  of  nitric  or  sulphuric  acids. 

219.  Bismuth  and  Chlorine.  —  Only  one  conipound  of  bis- 
muth and  chlorine  is  known,  BiCl3,  and  this  may  be  obtained 
either  by  passing  chlorine  over  the  metal,  by  distilling  the  metal 
with  corrosive  sublimate,  or  by  distilling  the  residue  obtained 
when  a  solution  of  the  metal  in  aqua-regia  is  evaporated  to  dry- 
ness.     The  product  in  either  case  is  a  very  fusible  and  volatile 
solid  resembling  the  corresponding  compound  of  antimony.     It 
dissolves  in  hydroehloric  acid,  but  is  decomposed  by  water  into 
hydrochloric  acid  and  insoluble  oxychloride  of  bismuth,  Bi  0  Cl. 
The  same  oxychloride  is  precipitated  when  a  solution  of  bismu- 
thous  nitrate  is  poured  into  a  solution  of  common  salt.     It  is  a 
brilliant  white  powder,  known  under  the  name  of  pearl  white, 
and  much  used  as  a  cosmetic.     It  is  insoluble  in  tartaric  acid, 
ammonic  sulphide,  or  solution  of  potash,  and  is  thus  distinguished 


§220.]  BISMUTH.  277 

from  oxychloride  of  antimony  precipitated  under  similar  condi- 
tions. Bismuthous  chloride  combines  with  hydrochloric  acid 
and  the  alkaline  chlorides  to  form  double  salts,  and,  like  SbCl^ 
may  be  mixed  with  concentrated  solutions  of  these  compounds 
without  undergoing  decomposition. 

The  compounds  of  bismuth  with  bromine,  iodine,  and  fluorine 
are  BiBr^  Bil^  and  BiFl* 

220.  Bismuth  and  Oxygen.  —  Metallic  bismuth  does  not 
tarnish  in  the  air,  but  at  a  red  heat  the  melted  metal  slowly 
oxidizes,  and  before  the  compound  blow-pipe  it  burns  brilliantly. 
The  product  of  the  oxidation  is  Bismuthous  Oxide,  Bi203.  The 
same  compound  is.  obtained  by  heating  the  nitrate  to  a  low  red 
heat.  It  is  a  pale  yellow  powder,  which  melts  at  a  full  red  heat 
to  a  dark  yellow  liquid.  It  is  insoluble  in  water,  and  will  not 
directly  combine  with  it;  but  by  pouring  a  solution  of  bismu- 
thous  nitrate  in  dilute  nitric  acid  into  dilute  aqua  ammonia,  or 
into  a  solution  of  potassic  hydrate,  a  white  hydrate  of  the  metal 
is  precipitated.  This  hydrate,  when  dried,  has  the  composition 
BiO-O-H;  but  there  are  reasons  for  believing  that  the  precip- 
itate falls  of  the  composition  Bi^O^H^.  By  a  gentle  heat,  or 
by  boiling  with  caustic  alkalies,  all  the  water  is  expelled  and 
Bi20*  is  left.  Bismuthous  oxide  is  a  decided  basic  anhydride. 
It  is  dissolved  by  hydrochloric,  nitric,  and  sulphuric  acids,  form- 
ing definite  salts.  Nevertheless,  by  fusing  the  oxide  with  sodic 
carbonate,  an  unstable  compound  is  obtained,  in  which  the 
metal  is  the  basic  radical  (Na-O-BiO). 

By  passing  chlorine  through  a  solution  of  K-Q-H,  holding 
Bi20s  in  suspension,  a  red  deposit  is  obtained,  which  is  a  mix- 
ture of  bismuthie  acid,  H-0-BiOz,  and  bismuthic  anhydride, 


Bi203  +  (4K-0-H+  2CI-CI  +  Aq)  = 

IH-O-BiO,  +  (4KCI  +  ff20  +  Ag).  [227] 

The  two  products  may  be  separated  by  means  of  cold  nitric 
acid,  which  dissolves  only  the  anhydride.  Bismuthic  acid  dis- 
solves in  a  solution  of  potassic  hydrate,  giving  a  blood-red  solu- 
tion ;  but  the  salt  thus  formed  is  very  unstable  and  is  decom- 
posed by  mere  washing.  The  other  compounds  of  the  acid  are 
little  known.  At  a  temperature  of  130°  the  red-colored  acid  is 
resolved  into  water  and  the  brown  anhydride. 


278  BISMUTH.  [§221. 

Bismuthic  anhydride,  when  gently  heated,  changes  into  an  in- 
termediate oxide,  Bi2  04,  or  rather  into  a  mixture  of  this  oxide 
and  Bi203.  If  heated  in  a  current  of  hydrogen,  it  is  at  once 
completely  reduced  to  the  lower  degree  of  oxidation.  When 
heated  with  sulphuric  or  nitric  acids  it  evolves  oxygen,  produ- 
cing bismuthous  sulphate  or  nitrate ;  and  when  heated  with  hy- 
drochloric acid  it  evolves  chlorine,  yielding  bismuthous  chloride. 

221.  Bismuthous  Nitrate,  Bi=03=(N02)3 .  5ff20,  is  the  most 
important  of  the  salts  of  bismuth.     It  forms  large  deliquescent 
crystals.     It  readily  dissolves  in  water  strongly  acidified  with 
nitric  acid,  but  when  mixed  with  a  large  volume  of  water  it  is 
decomposed,  and  a  white  basic  salt  of  somewhat  variable  compo- 
sition, formerly  called  the  magistery  of  bismuth,  is  precipitated. 
The  first  precipitate  appears  to  consist  mainly  of  the  compound 
Bi=03=(N02)iIT2;  but  this  is  more  or  less  decomposed  by  the 
subsequent  washings.     The  product  is  now  generally  known  as 
the  basic  nitrate  of  bismuth,  and  is  used  medicinally. 

222.  Bismuthous  Sulphate.  —  When  bismuthous  oxide  dis- 
solves in  sulphuric  acid,  the  normal  sulphate  Bi2i  06i(S02)3  is 
undoubtedly  formed ;  but  when  the  solution  is  evaporated  this 
salt  loses  the  larger  part  of  its  acid,  and  the  yellow  product 
obtained,  when  the  residue  is  gently  heated,  has,  approximately 
at  least,  the  composition  (BiO)2=02=S02;  although,  being  easily 
decomposed  by  heat,  it  is  difficult  to  obtain  the  compound  in  a 
pure  condition.     The  formula  of  the  basic  nitrate  may  also  be 
written  BiO-0~N02.  ff20,  and  the  formation  of  salts  of  this 
type  is  characteristic  of  the  class  of  elements  we  are  studying. 

223.  Bismuth  and  Sulphur.  —  The  native  compound  of  bis- 
muth and  sulphur  already  mentioned,  Bi2S3,  is  isomorphous  with 
antimony  glance,  Sb2S&  which  it  closely  resembles.     The  same 
compound  may  be  obtained  by  fusing  bismuth  with  sulphur  in 
proper  proportions,  and  also  by  passing  H2S  through  the  solu- 
tion of  a  bismuth  salt.     The  precipitated  sulphide  is  black,  and 
is  not  dissolved  by  alkaline  hydrates  or  sulpho-hydrates.     It  is 
also  insoluble  in  all  the  dilute  mineral  acids,  but  it  dissolves  in 
hot  nitric  acid.     When,  however,  the  solution  is  mixed  with 
water,  most  of  the  bismuth  is  again  precipitated  as  basic  nitrate. 
When  heated  in  the  air,  Bi^  is  oxidized  and  yields  S02  and 
Bi20s,  which  melts  to  dark  yellow  globules.     Bismuthous  sul- 
phide is  a  sulpho-anhydride,  and  the  following  minerals  may  be 
regarded  as  sulpho-bismuthites :  — 


§224.]  QUESTIONS  AND  PROBLEMS.  279 


Kobellite  Orthorhombic  ? 

Needle  Ore  «  ([  Cu^PbJ  IS6L 

Wittichenite  " 

Emplectite  " 

224.  Characteristic  Reactions.  —  The  decomposition  of  the 
soluble  salts  of  bismuth  by  water,  with  the  formation  of  an  in- 
soluble basic  salt,  is  the  most  characteristic  reaction  of  this 
metal.  The  salts  of  bismuth  are  easily  reduced  on  charcoal 
before  the  blow-pipe,  and  yield  a  metallic  bead,  surrounded  by 
a  yellow  coating  of  oxide. 

Questions  and  Problems. 
Nitrogen. 

1.  In  order  to  determine  the  composition  of  the  air,  863.7  cTm.8 
of  air  measured  under  a  pressure  of  55.76  c.  m.,  and  at  5°.5,  were 
mixed  in  an  eudiometer-tube  with  a  quantity  of  pure  hydrogen. 
After   addition  of  hydrogen  the  volume  measured  1006.7  cT^a".8, 
under  pressure  of  69.11  c.  m.     The  mixture  was  next  exploded 
by  an  electric  spark,   and   after  the  explosion  the  residual  gas 
measured  800.7  cTnT.3,  under  a  pressure  of  49.14  c.  m.,  and  at  5°.6. 
Required  composition  of  air  by  volume  in  100  parts. 

Solution.  By  [4]  and  [9]  it  will  be  found  that  the  three  volumes 
given  above  would  have  measured,  under  the  normal  condi- 
tions, respectively  621.20,  897.38,  and  507.38.  The  absorption 
due  to  the  combustion  of  the  hydrogen  is  then  897.3  — 507.3 
=  390  cTlm:8  Of  this  £  or  130  was  oxygen.  Hence  621.20 
cTm.3  of  air  contained  130  cT^f.8  of  oxygen  and  491.2  c7~m.8 
of  nitrogen,  or  100  parts  contained  20.92  oxygen  and  79.08 
nitrogen. 

2.  In  another  experiment  885.4  cTnF.3  of  air  at  53.88  c.  m.,  and 
0°.5  were  taken.     After  addition  of  hydrogen,  volume  measured 
1052.7  c.  m.8,  at  70.31  c.  m.  and  0°.5.     After  explosion  the  volume 
was  reduced  to  858.3   c.  m.8,  at  51.36  c.  m.  and  0°.5.     Required 
composition  of  air  by  volume  in  100  parts. 

Ans.  Oxygen  20.93,  nitrogen  79.07. 

3.  One  cubic  metre  of  dry  air,  measured  under  normal  conditions, 
was  passed  over  ignited   copper-turnings.      How  much  must  the 
copper  have  increased  in  weight  ?  Ans.  299.9  grammes. 

4.  In  preparing  nitrogen  gas  by  [132],  what  volume  of  nitrogen 
is  obtained  for  every  litre  of  chlorine  used  ?          Ans.  4  of  a  litre. 


280  QUESTIONS  AND  PEOBLEMS. 

5.  What  weight  of  nitric  acid,  Sp.  Gr.  =  1.47,  can  be  made  from 
1 70  kilos,  of  soda  nitre,  and  what  weight  of  sulphuric  acid  must  be 
used  in  the  process  ?  [135.] 

Ans.  196  kilos,  of  sulphuric  acid,  152.4  nitric  acid. 

6.  When,  in  the  preparation  of  nitric  acid,  two  molecules  of  nitre 
are  used  to  each  molecule  of  sulphuric  acid,  one  half  of  the  nitric 
acid  is  given  off  with  great  readiness ;  but  to  obtain  the  second  half 
we  must  heat  the  materials  to  a  much  higher  temperature.     In  the 
first  stage   of  the  reaction  sodic  bisulphate  is  formed,  and  in  the 
second,  neutral  sodic  sulphate.     Write  the  two  successive  reactions. 

7.  How  much  sulphuric  acid  is  required  for  the  decomposition  of 
303.3  grammes  of  potassic  nitrate  ?  Ans.  294  grammes. 

8.  Write  the  reaction  of  nitric  acid  on  sulphur,  assuming  that 
the  products  are  sulphuric  acid  and  nitric  oxide. 

9.  Write  the  reaction  of  nitric  acid  on  copper,  assuming  that  the 
products  are  cupric  nitrate  and  nitric  oxide. 

10.  How  much  nitric  acid  (Sp.  Gr.  1.228)  is  required  to  dissolve 
14.7  grammes  of  copper  ?  Ans.  107.6  grammes. 

11.  How  much  to  dissolve  16.7  grammes  cupric  oxide  ? 

Ans.  73.21  grammes. 

12.  A  quantity  of  plumbic  nitrate,  weighing  0.993  grammes,  yields 
on  ignition  0.669  gramme  of  plumbic  oxide.     By  another  determi- 
nation it  appears  that  1.324  grammes  of  the  same  salt,  ignited  in  a 
glass   tube  with   copper-turnings,   yield    89.34  cTnT3   of  nitrogen. 
Deduce   the   percentage   composition   and   symbol   of  nitric   acid, 
assuming  that  the  composition  of  plumbic  oxide  and  the  atomic 
weight  of  lead,  oxygen,  and  nitrogen  are  known.    What  reason  have 
you  for  assuming  that  the  acid  molecule  contains  only  one  atom  of 
hydrogen  ? 

13.  Write  the  reaction  of  nitric  acid  on   phosphorus,  assuming 
that  phosphoric  acid  and  one  or  more  of  the  oxides  of  nitrogen  are 
the  products  of  the  reaction. 

14.  Write  the  reaction  of  nitric  acid  on  cotton.     (31.) 

15.  Illustrate  by  means  of  a  table  the  relations  of  the  various 
acids  and   anhydrides  which   may  be  theoretically  derived   from 
orthonitric  acid. 

16.  In  nitric  acid  and  the  nitrates,  what  is  the  quanti valence  of 
nitrogen  ? 

1 7.  In  nitrous  acid  and  the  nitrites,  what  is  the  quantivalence  of 
nitrogen  ? 


QUESTIONS  AND  PEOBLEMS.  281 

18.  Illustrate  by  means  of  a  table  the  relations  of  the  various 
acids   and   anhydrides  which   may  be   theoretically  derived   from 
orthonitrous  acids. 

19.  Can     nitrite  ever  be  isomeric  "with  a  nitrate  ?     What  is  the 
essential  difference  between  the  two  classes  of  compounds  ? 

20.  The  0p.  (f5»r.  of  nitric  peroxide  vapor  referred  to  air  has 
been  found  to  be  1.72.    How  does  this  value  agree  with  the  number 
deduced  from  theory  ? 

21.  With  what  folumes  of  oxygen  gas  must  one  litre  of  nitric 
oxide   be   mixed,  to  prepare  respectively  nitrous  anhydride  and 
nitric  peroxide  ? 

22.  The  Sp.  Gr.  of  nitric  peroxide  would  seem  to  compel  us  to 
assign  to  the  compound  the  symbol  we  have  adopted,  and  the  same 
group  of  atoms  also  constantly  acts  as  a  univalent  radical.     Can 
you  harmonize  these  facts  with  the  theory  of  (69)  ? 

23.  What  volume  of  oxygen  is  required  to  convert  3  grammes  of 
nitric  oxide  (in  presence  of  water)  into  nitric  acid  ? 

Ans.   1674.6  c7^.8 

24.  Write  the  reaction  of  nitric  peroxide  on  calcic  hydrate. 

25.  In  the  preparation  of  nitric  oxide  by  [152],  why  should  you 
anticipate  that  nitrous  oxide,  or  even  nitrogen  gas  might  be  evolved, 
when  the  nitric  acid  was  nearly  exhausted1? 

26.  Analyze  the  reaction  [152],  and  represent  the  two  stages  by 
separate  equations. 

27.  Analyze  the  reaction  [153],  and  determine  the  amounts  of  the 
different  factors  which  should  be  used  in  order  to  make  10  litres  of 
nitric  oxide  gas. 

28.  Write  the  reaction  when  ferrous  sulphate,  sulphuric  acid,  and 
nitre  are  heated  together. 

29.  The  gp.  (g>£.  of  nitric  oxide  referred  to  air  is  1.038.     How 
does  this  compare  with  the  theoretical  number  ? 

30.  When  sodium  is  heated  in  a  confined  quantity  of  NO,  the 
volume  of  the  gas  is  reduced  to  one  half,  and  the  residue  is  found 
to  be  pure  nitrogen.     Assuming  that  the  Sp.  Gr.  is  known,  show 
that  this  fact  proves  that  the  symbol  we  have  assigned  to  the  com- 
pound must  be  correct. 

81.  Analyze  reaction  [154],  and  show  in  what  it  differs  from  [133]. 

32.  What  weight  and  what  volume  of  nitrous  oxide  can  be  ob- 
tained from  240  grammes  of  ammonic  nitrate  ? 

Ans.  132  grammes,  or  66.9  litres. 


282  QUESTIONS  AND  PEOBLEMS. 

33.  One  litre  of  nitric  oxide  gas  will  yield  by  [155]  what  volume 
of  nitrous  oxide  ?  Ans.  \  litre. 

34.  Analyze  reaction  [156],  and  represent  the  two  stages  by  sep- 
arate equations. 

35.  What  evidence  is  given  that  nitrous  oxide  is  less  stable  than 
nitric  oxide  ? 

36.  When  sodium  is  heated  in  nitrous  oxide  no  change  of  volume 
results,  and  the  residue  is  pure  nitrogen.     The  Sp.  Gr.  of  nitrous 
oxide  is  22.     Deduce  from  these  facts  the  symbol  of  the  compound. 

37.  What  volume  of  gas  would  a  litre  of  nitrous  oxide  yield  when 
decomposed  by  heat  ?  Ans.  \\  litres. 

38.  What  is  the  quantivalence  of  nitrogen  in  nitrous  oxide,  and 
what  in  nitric  oxide  ? 

39.  What  are  the  relations  of  the  oxychlorides  of  nitrogen  to  the 
oxides  ? 

40.  What  strong  reason  may  be  adduced  for  doubling  the  formula 
of  nitric  oxydichloride  ?     Would  not  the  same  principle  require  us 
to  double  the  symbols  of  two  of  the  oxides  ?  and  what  argument 
can  you  urge  in  favor  of  the  symbols  adopted  in  this  book  ? 

41.  What  is  the  specific  gravity  of  ammonia  gas  referred  to  air, 
and  referred  to  hydrogen  ?  Ans.  0.591,  and  8.5. 

42.  What  would  be  the  volume  of  3.0464  grammes  of  ammonia 
gas  at  273°.2  and  38  c.  m.  ?  Ans.  16  litres. 

43.  What  weight  of  ammonia  would  be  obtained  from  one  litre 
of  NO  by  reaction  [160]  ?  Ans.  0.7614  grammes. 

44.  Ammonia  gas  may  also  be  formed  by  the  action  of  metallic 
zinc  (when  in  contact  with  platinum  or  iron)  on  a  mixture  of  a 
nitrate  with  a  solution  of  potash.     Write  the  reaction  [161]. 

45.  In  order  to  determine  the  amount  of  nitric  acid  present  in  a 
specimen  of  crude  soda  nitre,  1.000  gramme  was  treated  as  in  the 
last  reaction.     The  ammonia  evolved  was  conducted  into  a  solution 
of  hydrochloric  acid,  and  subsequently  precipitated  with   platinic 
chloride.     This  precipitate  weighed  2.101 7  grammes.     What  was  the 
per  cent  of  pure  soda  nitre  ?  Ans.  80%. 

46.  In   order   to   obtain    10   litres  of  ammonia  gas,  how  many 
grammes  of  sal  ammoniac  must  be  taken  ?  Ans.  23.96. 

47.  What  volume  of  nitrogen  would  be  formed  by  burning  one 
litre  of  ammonia  ?     Write  the  reaction.  Ans.  ^  litre. 

48.  When  an  organic  substance  is  heated  with  soda  lime  (a  mix- 


QUESTIONS  AND  PROBLEMS. 

ture  of  caustic  soda  and  lime),  all  the  nitrogen  present  is  evolved  as 
ammonia,  which  may  be  collected  in  hydrochloric  acid  and  com- 
bined with  platinic  chloride  as  above.  In  a  given  determination 
the  weight  of  the  precipitate  thus  obtained  was  2.232  grammes. 
What  was  the  weight  of  nitrogen  in  the  compound  ? 

Ans.  0.140  grammes. 

49.  Deduce  from  the  results  of  the  eudiometric  experiments  de- 
scribed on  page  241  the  symbol  of  ammonia  gas.     Must  we  know 
the  specific  gravity  in  order  to  fix  the  formula  definitely  ? 

50.  Show  that  the  result  of  the  experiment  with  chlorine  gas 
confirms  the  formula  just  deduced. 

51.  Write  the  symbols  of  the  different  amines  according  to  the 
plan  of  (29). 

52.  The  amides  may  be  derived  from  the  corresponding  acids 
through  what  replacement  ? 

53.  After  what  two  types  may  the  symbols  of  the  amides  be 
written  ? 

54.  Write  the  symbols  of  oxamic  and  succinamic  acids  after  the 
water  type. 

55.  Explain  the  meaning  of  the  terms  basic  and  alcoholic,  as 
applied  to  the  atoms  of  hydrogen. 

56.  Write  the  symbols  of  the  two  lactamides  after  the  ammonia 
type. 

57.  How  may  the  imide  and  nitrile  compounds  be  regarded  as 
constituted  on  the  type  of  ammonia  ? 

58.  The  nitriles  (170)  may  be  regarded  as  cyanides  of  what 
radicals  ? 

59.  Why  should  you  anticipate  that  the  imide  compounds  would 
have  an  acid,  and  the  nitrile  compounds  a  basic  character? 

60.  Write  the  reactions  which  take  place  when  acetic,  benzoic, 
lactic,  and  oxalic  acids  combine  with  ammonia. 

61.  Write  the  reactions  corresponding  to  [174  and  175],  using  the 
sodium  instead  of  the  ammonium  salts. 

62.  What  proof  do  you  have  that  ammonium  is  a  univalent  rad- 
ical? 

63.  What  per  cent  of  NH3  does  the  platinum  salt  contain  ? 

64.  When  aqua  ammonia  is  added  to  a  solution  of  ferric  chloride, 
(Fe»)Clv  ferric  hydrate,  (Pe^Ho^,  is  precipitated.     Write  the  re- 
action. 


284  QUESTIONS  AND  PEOBLEMS. 

65.  Write  two  reactions  in  which  aqua  ammonia  acts  like  a  solu- 
tion of  caustic  soda,  and  two  others  in  which  it  does  not. 

66.  Write  the  reaction  which  takes  place  when  a  mixture  of  am- 
monic  chloride  with  calcic  carbonate  is  sublimed. 

67.  Write  the  reaction  by  which  the  sublimed  carbonate  when 
exposed  to  the  air  changes  to  the  acid  carbonate. 

68.  When  a  solution  of  ammonic  chloride  is  boiled  with  a  solution 
of  caustic  soda,  ammonia  gas  is  evolved.     Write  the  reaction. 

69.  Write  the  symbols  of  the  compounds  formed  by  the  union  of 
the  amines  described  in  (167),  both  with  hydrochloric  acid  and  with 
water. 

70.  Write  the  symbol  of  the  ammonium  base  which  contains  the 
radicals  phenyl,  C0£T6,  amyl,  C6HW  ethyl,  C2#6,  and  methyl,  CHy 

71.  Show  what  different  compounds  may  be  formed  by  the  dehy- 
dration of  the  acetate,  lactate,  and  oxalate  of  ammonia. 

Phosphorus. 

72.  The  Sp.  Gr.  of  phosphorus  vapor  has  been  observed  to  be 
63.8,  and  according  to  Deville  no  material  change  is  effected  by  a 
temperature  of  1,040°.     Moreover,  the  specific  gravities  of  the  va- 
pors of  the  following  compounds  have  been  determined,  and  also 
the  per  cent  of  phosphorus  which  they  contain. 

c      «  Per  cent  of 

Phosphorus. 

Phosphuretted  Hydrogen,  17.1  91.18 

Phosphorous  Chloride,  68.4  22.55 

Phosphoric  Oxychloride,  76.6  20.19 

Given  these  results  of  observation,  show  how  the  atomic  weight  of 
phosphorus  and  the  molecular  constitution  of  the  elementary  sub- 
stance may  be  determined. 

73.  The  atomic  weight  of  phosphorus,  now  received,  was  found 
by  burning  a  known  weight  of  red  phosphorus  in  perfectly  dry  air, 
and   weighing  the  phosphoric  anhydride  thus  formed.     Assuming 
that  one  gramme  of  phosphorus  yields  2.2903  grammes  of  phosphoric 
anhydride,  what  must  be  the  atomic  weight  of  phosphorus?     How 
far  does  this  experiment  modify  the  conclusion  reached  in  the  last, 
problem  ? 

74.  How  much  phosphorus  can  be  obtained  from  9.3  kilos,  of  pure 
calcic  phosphate  by  [179]  ?  Ans.  1.24  kilos. 

75.  Can  you  discover  any  connection  between  the  difference  of 
specific  heat  of  the  two  varieties  of  phosphorus,  and  the  difference 


QUESTIONS  AND  PROBLEMS  285 

of  calorific  power  ?     Does  the  first  difference  wholly  explain  the 
last? 

76.  Show  that  ortho-  and  meta-phosphoric  acid  may  be  derived 
from  the  assumed  pentatomic  acid  by  successive  dehydration,  and 
make  a  table  which  shall  exhibit  the  different  possible  derivatives 
of  this  compound. 

77.  Taking  orthophosphoric  acid  as  the  starting-point,  in  place  of 
the  assumed  pentatomic  acid,  show  how  the  different  varieties  of 
phosphoric  acid  may  be  deduced. 

78.  What  is  the  basicity  of  phosphorous  and  hypophosphorous 
acid's  ?  and  what  is  the  quantivalence  of  phosphorus  in  these  com- 
pounds ? 

79.  When  either  phosphorous  or  hypophosphorous  acids  are  heat- 
ed, they  break  up  into  orthophosphoric  acid  and  PHy     Write  the 
reaction  in  each  case. 

80.  Compare  together  the  nitrates  and  phosphates  of  the  univa- 
lent  and  bivalent  metallic  radicals. 

81.  Write  the  reaction  of  a  solution  of  argentic  nitrate  on  a 
solution  of  common  sodic  phosphate,  and  show  why,  after  precipita- 
tion, the  solution  must  be  acid. 

82.  Write  the  reaction  which  takes  place  when  common  sodic 
phosphate  is  heated  to  redness. 

83.  Write  the  reaction  of  a  solution  of  argentic  nitrate  on  a  solu- 
tion of  sodic  pyrophosphate.     If  the  first  salt  is  used  in  excess,  why 
must  the  solution  after  the  precipitation  be  neutral  ? 

84.  Pyrophosphoric  acid  may  be  prepared  by  first  adding  plum- 
bic  acetate  to  a  solution   of  sodic  pyrophosphate,  when  plumbic 
pyrophosphate  is  precipitated,  and  then  decomposing  this  precipi- 
tate suspended  in  water  with  H2S.     The  solution  thus  obtained 
evaporated  in  vacuo  gives  crystals  of  the  compound.     Write  the 
reactions.     Why  may  not  the  solution  be  evaporated  by  heat  in  the 
usual  way  ? 

85.  Write  the  reaction  which  takes  place  when  PH3  burns. 

86.  Write   the   symbols   of  Trimethyl-phosphine ;    Tetramethyl- 
phosphonium  Hydrate  ;  Trimethyl-amyl-phosphonium  Iodide. 

87.  Write  the  symbols  of  the  platinum  and  gold  salts  of  tetra- 
ethyl-phosphonium.     (136)   (147). 

88.  Write  the  symbols  of  Triethyl-phosphine  Oxide  and  Triethyl- 
phosphine  Iodide.     How  does  the  last  differ  from  Triethyl-phospho- 
nium  Iodide  ? 


286  QUESTIONS  AND  PROBLEMS. 

89.  Explain  the  use  of  PCl&  as  a  reagent,  and  give  illustrations 
of  its  peculiar  action. 

90.  Can  you  devise  a  method  by  which  the  reaction  [183]  may 
be  applied  in  the  preparation  of  phosphorous  acid  ? 

91.  Does  the  reaction  [186]  throw  any  light  on  the  constitution 
of  phosphoric  acid  ? 

92.  What  different  degrees  of  quanti valence  does   phosphorus 
manifest  in  the  compounds  described  above  ?      Point  out  the  ex- 
amples of  each  condition. 

93.  Make  a  summary  of  the  resemblances  and  differences  be- 
tween the  compounds  of  nitrogen  and  those  of  phosphorus. 

Arsenic. 

94.  Represent  by  graphic  symbols  the  constitution  of  Mispickel, 
and  show  how  it  is  possible  that  the  double  atom  of  sulphur  should 
replace  the  double  atom  of  arsenic. 

95.  What  should  be  theoretically  the  specific  gravity  of  arsenic 
vapor  referred  to  air  ?  Ans.  10.4. 

96.  Compare  together  the  formulas  of  nitrous  and  arsenious  acids, 
and  point  out  their  relations  to  each  other.     Is  phosphorous  acid 
allied  to  the  other  two  ? 

97.  Write  the  reactions  by  which  cupric  and  argentic  arsenites 
are  formed. 

98.  Write  the  symbols  of  the  three  hydrates  of  arsenic  acid,  and 
give  their  names,  following  the  analogy  of  phosphoric  acid. 

99.  If  the  arseniates  [190]  are  heated  until  all  the  water  is 
expelled,  what  will  be  the  symbols  of  the  compounds  left  ? 

100.  Write  the  reaction  of  argentic  nitrate  on  a  solution  of  either 
of  the  compounds.     [190.] 

101.  Write  the  reaction  of  a  solution  of  magnesic  sulphate  and 
ammonia  on  a  solution  of  either  of  the  compounds.     [190.] 

102.  State  the  differences  between  phosphoric  and  arsenic  acids. 

103.  Write  the  reaction  which  takes  place  when  H3As  burns, 
both  with  a  sufficient  and  with  a  limited  supply  of  oxygen. 

104.  How  may  the  reactions  described  in  (197)  be  used  to  detect 
the  presence  of  arsenic  in  a  suspected  liquid  ? 

105.  How  could  you  discover  the  presence  of  the  arsenic  acid 
formed  by  reaction  [193]  ? 


QUESTIONS  AND  PROBLEMS.  287 

106.  State  the  resemblances  and  differences  between  the  amines, 
the  phosphines,  and  the  arsines. 

107.  Is  the  quanti valence  of  arsenic  the  same  in  all  the  com- 
pounds of  kakodyl ? 

108.  In  what  respects  does  kakodyl  resemble,  and  in  what  does 
it  differ  from,  the  corresponding  compound  of  phosphorus  ? 

109.  Does  the  relation  of  arsenic  to  chlorine  differ  materially 
from  the  relation  of  phosphorus  to  the  same  element '? 

110.  Write  the  reaction  of  HZS  on  a  solution  of  As203  in  dilute 
hydrochloric  acid. 

111.  Analyze  the  reactions  [195]  and  [196],  and  give  the  names 
of  the  products  which  are  formed. 

112.  What  would  be  the  chemical  names  of  the  minerals  Prous- 
tite  and  Enargite,  and  what  are  the  corresponding  oxygen  com- 
pounds ?     Define  the  class  of  compounds  to  which  these  minerals 
belong. 

Antimony. 

113.  Why  is  the  molecular  weight  of  antimony  doubtful? 

114.  Theoretically,  what  weight  of  metallic  antimony  should  be 
obtained  from  1,020  kilos,  of  antimony  glance  ?       Ans.  732  kilos. 

115.  The  most  common  impurities  of  commercial  antimony  are 
arsenic,  iron,  copper,  and  lead.     Why  should  the  process  described 
(206)  tend  to  remove  these  substances  ? 

116.  Write  the  reaction  when  antimony  burns. 

117.  Write  the  reaction  of  nitric  acid  on  antimony,  assuming 
that  the  products  are  Sba04  and  NO. 

118.  Write  the  reaction  of  hydrochloric  acid  on  Sb^Ss.     What 
will  prevent  the  resulting  solution  from  becoming  turbid  when 
mixed  with  water  ? 

119.  What  should  be  theoretically  the  Sp.  Gr.  of  SbClJ 

120.  Why  is  it  probable  that  the  double  chlorides  (207)   are 
molecular  compounds  ? 

121.  When  SbCl3  is  mixed  with  strong  HCl  -f-  Aq,  what  com- 
pound would  analogy  lead  us  to  suppose  is  formed  in  the  solution  ? 

122.  Write  the  reaction  of  chlorine  gas  (in  excess)  on  antimony 
and  on  Sb  C78. 

123.  Write  the  reaction  of  water  on  SbBr3  and  SW8. 


288  QUESTIONS   AND   PROBLEMS. 

124.  Write  the  reactions  when  Sbz03  dissolves  in  HCl-\-Aq  and 
HZSO±.     [202.] 

125.  Write  the  reaction  when  Sb203  dissolves  in  cream  of  tartar. 

126.  Write  the  reaction  when  tartar  emetic  is  heated  to  200°. 

127.  Write  the  symbols  of  the  compounds  formed  by  dissolving 
AszOz,  Asfiv  or  Bispfr  in  cream  of  tartar. 

128.  Write  the   symbols  of  the  compounds  of  the  same  class 
derived  from  FezO#  CV203,  and  BZ0^  assuming  that  the  radicals 
FezOz,  O202,  and  BO  replace  the  SbO  of  tartar  emetic. 

129.  Write  the  reaction  when  to  a  solution  of  tartar  emetic  is 
added  a  solution  of  calcic  chloride,  knowing  that  the  corresponding 
lime  compound,  being  insoluble,  is  precipitated.     Calcium,  it  must 
be  remembered,  takes  the  place  of  two  atoms  of  potassium. 

130.  Write  the  symbol  of  diaceto-diethylic  tartrate. 

131.  State  the  grounds  for  the  distinction  between  the  three  sets 
of  hydrogen  atoms  which  tartaric  acid  contains.     By  what  names 
do  you  distinguish  the  different  sets  of  atoms,  and  what  other  ex- 
amples have  been  studied  in  which  a  similar  distinction  has  been 
made  ? 

132.  What  is  the    name    of  the    compound    H2,K2=OfSb203? 
Write  the  reaction  of  a  solution  of  this  reagent  upon  a  solution 
ofNaCl. 

133.  On  boiling  its  solution,  the  acid  potassic  pyroantimoniate 
changes  into  a  metantimoniate  which  does  not  precipitate  soda. 
Write  the  reaction. 

134.  Write  the  reaction  off(HCl-{-Aq)  on  ZnsSby  assuming 
that  the  product  is  HaSb. 

135.  Write  the  symbols  of  the  ethyl  and  amyl  compounds  of 
antimony,  following  the  analogy  of  the  methyl  compounds  whose 
symbols  are  given. 

136.  Write  the  reaction  of  triethyl-stibine  on  hydrochloric  acid. 

137.  Represent  by  graphic  symbols  the  constitution  of  ZnaSbt 
and  ZnzSbz,  and  give  the  symbols  of  other  compounds  formed  after 
the  same  type. 

138.  Write  the  reaction  when  antimonious  oxide  and  sulphur  are 
melted  together. 

139.  Write  the  reaction  when  H2S  is  passed  through  a  solution  of 
tartar  emetic. 

140.  Analyze  reactions  [221],  [222],  and  [223],  and  name  the 
classes  of  compounds  to  which  the  several  products  belong. 


QUESTIONS  AND  PROBLEMS.  289 

141.  Show  by  symbols  the  relations  of  the  assumed  sulphur  acids 
to  which  the  several  sulphantimonites  are  referred. 

142.  Explain  the  distinction  between  a  chemical  compound  and 
a  molecular  aggregate.     What  different  orders  of  combination  do 
the  facts  and  the  atomic  theory  require  of  us  to  assume  in  such  a 
mineral  as  Tetrahedrite  ? 

143.  How  are  the  phenomena  of  isomorphous  substitution  in  the 
mineral  kingdom  to  be  explained  in  harmony  with  the  atomic 
theory  ? 

144.  Write  the  reaction  of  H^S  on  a  solution  of  SbCl&. 

145.  Write  the  reaction  of  hydrochloric  acid  on  the  precipitate 
obtained  by  the  last  reaction. 

Bismuth. 

146.  Represent  by  graphic  symbols  the  constitution  of  Bismuth 
Glance,  and  Tetradymite. 

147.  Compare  the  qualities  of  metallic  bismuth  with  those  of  the 
other  elementary  substances  belonging  to  the  same  series,  consider- 
ing especially  the  crystalline  form  and  the  specific  gravity. 

148.  Write  the  reaction  of  nitric  acid  on  bismuth,  and  compare* 
this  reaction  with  that  of  nitric  acid  on  antimony. 

149.  Write  the  reaction  of  aqua-regia  on  bismuth. 

150.  Compare  the  compounds  of  the  alcohol  radicals  with  the 
different  members  of  the  nitrogen  series  of  elements,  and  present 
the  subject  in  a  written  form. 

151.  Write  the  different  reactions  by  which  BiCla  may  be  formed* 

152.  Write   the  reaction  of  water  on  BiCl#  and  the  reaction 
when  a  solution  of  bismuthous  nitrate  is  poured  inta  a  solution  of 
common  salt. 

153.  Why  does  the  presence  of  a  large  amount  of  H±NCl  prevent 
a  solution  of  BiCl3  from  becoming  turbid  when  mixed  with  water? 

154.  Compare  BiCl3  with  the  corresponding  chlorides  of  the  same 
series.     What  inference  do  you  draw  from  the  fact  that  the  com* 
pound  Bid^  has  not  been  obtained  ?     Have  any  other  facts  been 
mentioned  pointing  to  the  same  conclusion  ?     What  is  the  evidence 
that  bismuth  is  ever  quinquivalent  ? 

155.  Write  the  reaction  when  bismuth  burns>  or  is  more  slowly 
oxidized. 

156.  Write  the  reaction  when  bismuthous  nitrate  is  heated  to  a 

13  8, 


290  QUESTIONS  AND  PROBLEMS. 

low  red  heat.     Why  in  this  process  is  it  important  to  avoid  a  higher 
temperature  ? 

157.  Write  the  reaction  when  a  solution  of  bismuthous  nitrate 
(in  dilute  nitric  acid)  is  poured  into  a  solution  of  potassic  hydrate. 

158.  Write  the  reactions  when  bismuthous   oxide  dissolves  in 
hydrochloric,  nitric,  or  sulphuric  acid. 

159.  Compare  the  oxides  and  hydrates  of  the  elements  of  the 
nitrogen  series,  and,  by  tabulating  their  symbols,  show  that  their 
molecular  constitution  is  analogous.     Trace  also  the  variation  in 
their  properties  as  you  descend  in  the  series. 

160.  Write  the  reaction  of  water  on  bismuthous  nitrate,  assum- 
ing that  the  basic  salt  whose  symbol  is  given  above,  together  with 
free  nitric  acid,  are  the  resulting  products. 

161.  If  Bi2Ss  and  SbzSs  are  precipitated  together,  how  may  the 
two  be  separated  ? 

162.  Write  the  reaction  when  Bi2S3  is  roasted  in  a  current  of  air. 

163.  To  which  of  the  three  classes  of  salts,  distinguished  on  page 
273,  must  the  several  sulpho-bismuthites  be  referred  V 

164.  Compare  the  sulpho-salts  of  bismuth,  antimony,  and  arsenic, 
and  point  out  their  mutual  relations. 


Division  IX. 

225.  VANADIUM.  F==  51.21.  —  Trivalent  and  quinqui- 
valent. A  very  rare  element,  discovered  in  1830  in  the  iron 
ores  of  Taberg  in  Sweden.  It  has  since  been  found  associated 
with  the  iron  and  uranium  ores  of  other  localities,  and  more 
recently  it  has  been  found  in  considerable  quantities  in  certain 
remarkable  metalliferous  sandstone  beds  occurring  in  the  county 
of  Cheshire  in  England.  Vanadium  is  also  the  essential  con- 
stituent of  a  few  very  rare  minerals.  Of  these  the  most  impor- 
tant is  Vanadinite,  which  is  a  vanadate  of  lead,  and  so  closely 
resembles  the  native  phosphate  and  arseniate  of  the  same  metal 
as  to  leave  no  doubt  that  all  three  have  a  similar  molecular  con- 
stitution, and  hence  that  vanadium  is  a  perissad  element  like 
phosphorus  and  arsenic.  Thus  we  have  the  following  minerals, 
which  are  all  isomorphous  with  each  other :  — 

Apatite  (Oz5F)i*<99ix(P<9)3, 

Pyromorphite  (Pb&  01}  i*  09 


§225.]  VANADIUM.  291 


Mimetine 

Vanadinite  (P&5  Ol)  *0^(  V0)z. 

The  study  of  the  other  compounds  of  vanadium  leads  to  the 
same  conclusion,  and  shows  that  the  same  character  already  no- 
ticed in  Bismuth  and  Antimony  is  developed  in  this  element  to 
a  still  higher  degree.  The  lowest  oxide  of  vanadium,  VO,  is  a 
powerful  univalent  or  trivalent  radical,  and  combines  with  chlo- 
rine or  replaces  hydrogen  like  an  elementary  substance,  and 
almost  all  of  the  compounds  of  the  element,  formerly  known, 
and  which  can  be  directly  prepared  from  the  native  vanadates, 
are  compounds  of  this  radical,  now  called  vanadyl,  but  which 
was  for  a  long  time  mistaken  for  the  element  itself.  We  have, 
for  example,  (  VO)  (7/3,  a  yellow  fuming  volatile  liquid  boiling 
at  126°  7  with  Sp.  Gr.  =  1.84  and  Sp.  Gr.  =  88.2,  also 
(  VO)  (7/2  in  brilliant  green  tubular  crystals,  next  (  VO)  Cl,  a 
light  brown  powder,  and  lastly,  (  V0)2  Ol,  a  brownish  yellow 
powder  resembling  mosaic  gold.  The  true  chlorides  of  vana- 
dium can  only  be  prepared  from  the  metal  or  its  nitride,  and 
the  air  must  be  carefully  excluded  during  the  process.  The 
following  have  been  recently  described  by  Roscoe:  VCI&  a 
bright  apple  green,  solid  in  hexagonal  plates,  with  a  micacious 
lustre  ;  F073,  in  brilliant  tubular  crystals  with  color  of  peach 
blossoms  ;  and  VC14,  a  dark  reddish-brown  volatile  liquid,  boil- 
ing at  154°,  with  Sp.  Gr.  at  0°=  1.858  and  Sp.  Gr.  =  93.3. 
Roscoe  was  unable  to  obtain  the  pentad  compound. 

The  oxides  of  vanadium  are,  —  first,  V202  or  VO-VO,  ob- 
tained as  a  gray  metallic  powder  when  the  vapor  of  VO  Cls 
mixed  with  hydrogen  is  passed  over  red-hot  carbon.  It  dis- 
solves in  dilute  acids  with  the  evolution  of  hydrogen,  and  can- 
not be  deprived  of  its  oxygen  except  with  the  greatest  difficulty. 
Secondly,  F203,  obtained  as  a  black  powder  when  V205  is  re- 
duced by  hydrogen  at  a  red  heat.  It  is  insoluble  in  acids. 
Thirdly,  F204,  obtained  in  the  form  of  blue  shining  crystals  by 
allowing  V2  03  to  absorb  oxygen  from  the  air.  Fourthly,  V2  05, 
vanadic  anhydride,  a  brownish-red  crystalline  solid,  fusible  at  a 
red  heat,  and  sparingly  soluble  in  water.  The  solution  has  a 
yellow  color,  and  is  strongly  acid  ;  but  no  definite  hydrate  has 
been  described.  Vanadic  anhydride  dissolves  in  concentrated 
sulphuric  acid  when  boiling,  giving  a  dark  red  solution.  If 
this  is  diluted  with  fifty  times  its  volume  of  water,  and  heated 
with  metallic  zinc,  it  rapidly  changes  color,  passing  through  all 


292  VANADIUM.  [§225. 

shades  of  blue  and  green  until  it  attains  a  permanent  lavender 
tint.  To  each  of  these  shades  corresponds  a  certain  degree  of 
oxidation  of  the  dissolved  vanadium,  thus  bright  blue  to  V20^ 
green  to  VZ0^  and  lavender  to  V202-,  and  by  using  less  active 
reducing  agents  the  change  may  be  arrested  at  any  desired 
point.  The  lavender  solution  absorbs  oxygen  with  such  avidity 
as  "  to  bleach  indigo  and  other  vegetable  coloring  matters  as 
quickly  as  chlorine,  and  far  more  powerfully  than  any  other 
known  agent." 

From  vanadic  anhydride  we  derive  the  vanadates,  of  which 
there  appear  to  be  three  classes  corresponding  to  the  phosphates. 

1.  Metavanadates  as  in  NH^OV02  or  PfcOf  (  F02)2. 

Dechenite. 

2.  Pyro  vanadates  as  in  NafOf  F2<93  or  PbfOf( 

Descloizite. 


3.  Orthovanadates  as  in  NafOfVO  .  Uff20or  Ca^0 

Of  these  salts  the  metavanadates  are  the  most  and  the  ortho- 
vanadates  the  least  stable,  the  reverse  of  what  is  true  in  the 
case  of  the  phosphates. 

There  are  two  nitrides  of  vanadium,  VN  and  VNZ.  The 
first  is  a  black  powder  obtained  by  acting  on  (  VO)  C13  with  dry 
NffB.  Its  composition  has  been  determined  by  analysis,  and  it 
is  interesting  not  only  as  fixing  the  atomic  weight  of  the  metal, 
but  also  as  the  starting-point  from  which  the  true  chlorides 
of  vanadium,  and  the  metal  itself,  have  been  reached. 

Metallic  vanadium  has  been  obtained  by  reducing  VC12  W1'th 
hydrogen.  It  is  a  light  whitish-gray  powder,  which  under  the 
microscope  appears  as  a  brilliant  crystalline  metallic  mass  with 
a  silver-white  lustre.  This  metallic  powder  has  a  Sp.  Gr.  ==. 
5.5,  and  is  not  magnetic.  It  does  not  volatilize  or  fuse  when 
heated  to  redness  in  an  atmosphere  of  hydrogen.  It  does  not 
tarnish  in  the  air  or  decompose  water  at  the  ordinary  tempera- 
tures, but  when  thrown  into  a  flame  it  burns  with  brilliant  scin- 
tillations. It  does  not  dissolve  in  hydrochloric  acid  hot  or  cold, 
and  only  slowly  in  hot  sulphuric  acid,  but  nitric  acid  of  all 
strengths  attacks  it  with  violence.  It  is  not  acted  upon  by 
solutions  of  the  caustic  alkalies,  but  when  fused  with  sodic 
hydrate  hydrogen  gas  is  evolved  and  a  vanadate  formed.  It 
unites  directly  with  chlorine  gas  to  form  F(7/4,  and  with  nitro- 
gen gas  to  form  VN,  and  it  is  capable  of  absorbing  as  much  as 


§  226.]  URANIUM.  293 

1.3  per  cent  of  hydrogen  gas.  It  attacks  all  glass  and  porce- 
lain in  which  it  is  heated,  a  compound  of  silicon  and  the  metal 
being  formed.  It  yields  also  an  alloy  with  platinum,  and  for 
these  reasons,  as  well  as  on  account  of  its  very  great  avidity 
(when  heated)  for  both  oxygen  and  nitrogen,  it  has  been  one  of 
the  most  difficult  of  all  the  elements  to  isolate. 


Division  X. 

226.  URANIUM.  U=  120.  —  One  of ^he  rarer  elements. 
Always  found  in  nature  combined  with  oxygen,  chiefly  in 
Pitchblende,  which  is  essentially  the  compound  £^04,  and  in 
a  rare  mineral  called  Uranite.'  Of  the  last  there  are  two  vari- 
eties: the  first  is  a  phosphate  of  uranium  and  calcium,  and 
the  second  a  phosphate  of  uranium  and  copper. 

or 
\ 

In  many  of  its  chemical  characteristics,  uranium  very  closely 
resembles  vanadium.  Like  the  last  element,  it  forms  an  oxide, 

UO,  which  acts  as  a  univalent  radical,  replacing  hydrogen  and 
combining  directly  with  chlorine;  and  all  the  most  important 
stable  and  characteristic  compounds  of  uranium  may  be  re- 
garded as  compounds  of  this  radical.  Moreover,  U202,  like 

V2  02,  cannot  be  decomposed  by  the  ordinary  reducing  agents, 
and  was  formerly  mistaken  for  the  metal  itself.  Uranyl  acts 
both  as  a  basic  and  as  an  acid  radical.  Of  the  uranyl  com- 
pounds, the  most  important,  besides  the  native  phosphates  al- 
ready mentioned,  are  Uranyl  Chloride,  (  UO)  Cl,  Uranyl  Fluor- 
ide, (  UO)F,  Uranyi  Hydrate,  (UO}~0-H  (a  yellow  powder), 
Uranyl  Nitrate,  (t70)-0-N02.Sff20  (a  beautiful  yellow  salt, 
crystallizing  in  long  striated  prisms),  and  Uranyl-potassic  Sul- 
phate, K,((70)=02=S02.ff20;  and  to  these  may  be  added  a 
number  of  remarkable  double  salts,  which  may  be  formed  by 
the  union  both  of  the  chloride  and  the  fluoride  of  uranyl  with 
the  chlorides  or  fluorides  of  the  metals,  of  the  alkalies,  or  earths. 

[ndeed,  these  double  salts  are  a  characteristic  feature  of  ura- 

lium,  and  one  which  becomes  still  more  marked  in  the  next 

lenient,  Columbium. 


294  URANIUM.  [§226. 

If  to  a  solution  of  a  uranyl  salt  we  add  ammonia,  or  the  so- 
lution of  any  other  alkali  or  earth,  we  obtain  a  yellow  precipi- 
tate. This  is  not,  however,  as  might  have  been  expected,  the 
hydrate  of  uranyl,  but  a  compound  of  the  radical  with  the  alkali, 
in  which  uranyl  acts  as  an  acid  radical.  The  constitution  of 
these  compounds  is  not  well  understood,  but  they  are  probably 
mixtures  of  uranyl  hydrate  with  a  compound  of  the  form 
R-O-(UO).  The  so-called  yellow  uranium  oxide  of  commerce 
is  a  hydrate  thus  prepared,  retaining  about  two  per  cent  of  am- 
monia. All  these  uranyl  compounds  have  a  yellow  color,  and 
the  yellow  oxide  is  used  to  communicate  a  beautiful  and  pecu- 
liar yellow  to  glaSfe.  Glass  thus  colored,  and  the  transparent 
uranyl  salts,  are  to  a  high  degree  fluorescent. 

Judging  from  the  uranyl  compounds  alone,  we  should  con- 
clude that  uranium  was  a  perissad  closely  allied  to  vanadium 
and  the  nitrogen  group  of  elements ;  but  there  are  other  com- 
pounds of  uranium  which  do  not  readily  conform  to  this  theory. 
Thus  we  have  a  chloride,  UCl^  and  a  series  of  uranous  salts 
(all  having  a  green  color),  in  which  one  atom  of  the  metal  ap- 
pears to  combine  with  two  atoms  of  chlorine,  or  to  replace  two 
atoms  of  hydrogen.  These  would  seem,  on  the  other  hand,  to 
indicate  that  uranium  was  an  artiad  element  allied  to  iron ;  and 
the  important  fact  that  the  native  oxide,  U304,  is  isomorphous 
with  the  magnetic  oxide  of  iron  sustains  this  view.  Uranium 
thus  appears  to  stand  between  the  nitrogen  group  of  elements 
of  the  perissad  family  and  the  iron  group  of  the  artiad  family. 
It  belongs  in  a  measure  to  both,  and  its  compounds  may  be  in- 
terpreted according  to  the  one  or  the  other  plan  of  molecular 
grouping.  In  classing  it  with  the  perissads  we  merely  follow 
what  appear  to  be  its  normal  relations ;  but  others  may  reason- 
ably entertain  a  different  view,  and  further  investigation  is  re- 
quired to  determine  its  quantivalence.  Uranium  thus  illustrates 
very  forcibly  the  remarks  already  made  on  chemical  classifi- 
cation. (103.) 

Of  metallic  uranium  but  little  is  known.  It  has  been  ob^ 
tained  by  decomposing  the  chloride  UC12  with  potassium,  and 
appears  to  be  a  steel-white  metal  (Sp.  Gr.  =  18.4),  which  is 
slightly  malleable,  and  not  readily  oxidized  by  atmospheric 
agents.  If  heated,  however,  it  burns  in  the  air,  and  dissolves 
in  dilute  acids  with  the  evolution  of  hydrogen.  The  compounds 


§226.]  QUESTIONS  AND  PROBLEMS.  295 

of  uranium  have  found  but  few  applications  in  the  arts.  The 
"  yellow  oxide "  is  used,  as  already  stated,  for  coloring  glass, 
and  the  so-called  black  oxide  (£7405),  obtained  by  igniting  the 
nitrate,  is  employed  as  a  black  pigment  in  painting  on  porcelain. 
The  nitrate,  which  is  the  most  common  soluble  salt,  has  been 
thought  to  have  some  valuable  qualities  in  photography. 


Questions  and  Problems. 

1.  State  the  grounds  on  which  the  conclusion  in  regard  to  the 
atomicity  of  vanadium  is  based,  and  represent  by  .  graphic  symbol 
the  constitution  of  Vanadinite. 

2.  How  does  the  Sp.  Gr.  of  the  vapor  of  vanadic  oxytrichloride 
compare  with  the  theoretical  value  ? 

3.  It  has  been  shown  by  careful  analysis  that  the  above  chloride 
contains  61.276  per  cent  of  chlorine.     What  is  the  atomic  weight 
of  vanadyl,  and  what  that  of  vanadium?     Ans.  67.29,  and  51.29. 

4.  In  order  to  determine  the  atomic  weight  of  vanadium  from 
vanadic  anhydride,  Roscoe  reduced  VzO&  by  hydrogen  to  vanadic 
oxide,  F203.    Four  experiments  gave  the  following  results  :  — 

Weight  of  F2  O5  used.  Weight  of  F2  O3  obtained. 
1st,                         7.7397  grammes,  6.3827  grammes. 

2d,  6  5819         "  5.4296         " 

3d,  5.1895         "  4.2819         " 

4th,  5.0450         «  4.1614         " 

Deduce  the  atomic  weight  of  vanadium. 

5.  Berzelius  assigned  to  Yanadic  Anhydride  the  symbol  F03,  and 
to  Vanadyl  Chloride  the  symbol  VCly     On  this  hypothesis  he  found 
for  the  atomic  weight  of  vanadium,  by  the  method  of  the  last  prob- 
lem, the  value  137  (when  0  =  16),  which  would  be  reduced  to 
134.74  by  the  more  accurate  determinations  of  Roscoe.     State  the 
reasons  for  believing  that  the  true  atomic  weight  of  the  element  is 
51.21,  and  that  the  compounds  have  the  symbols  assigned  to  them 
above.      Show  how  far  these  conclusions  have  been  proved,  and 
point  out  the  cause  of  the  former  error. 

6.  State  the  grounds  for  classing  uranium  with  vanadium,  as  well 
as  the  reasons  which  might  be  urged  for  associating  it  with  iron,  and 
write  the  rational  symbols  of  the  uranium  compounds  on  the  as- 
sumption that  this  element  is  an  artiad. 


296  COLUMBIUM.  §227.] 


Division  XL 

227.  COLUMBIUM    (Niobium).     Cb  =  94.  — -  Pentad. 
This  element  forms  the  acid  radical  of  Pyrochlore,  Columbite, 
Samarskite,  Euxenite,  Aeschynite,    Fergusonite,  and   a    few 
other  rare  minerals.     They   are  all  compounds  of  columbic 
anhydride,    Cb20&    with    various    metallic     oxides,  —  among 
which  those  of  cerium,  yttrium,  and  their  associated  elements 
are  especially  to  be  distinguished.     The  columbium,  however, 
is  almost  invariably  replaced  to  a  greater  or  less  extent  by  tan- 
talum.    Columbite,  the  most  abundant  of  these  minerals,  has 
the  symbol  [Fe,Mn~\  =  02=([  Cb, Ta~\  02)2.     It  has  a  black  color,  a 
submetallic  lustre,  and  a  specific  gravity  from  5.4  to  6.5,  in- 
creasing as  the  proportion  of  tantalum  increases.     When  finely 
powdered  it  is  easily  decomposed  by  fusion  with  potassic  bisul- 
phate,  and  on  subsequently  boiling  the  fused  mass  with  water 
a  white  insoluble  residue  is  obtained,  which  consists  chiefly  of 
Cb205,  and  from  this  the  different  compounds  of  columbium 
may  be  prepared.     Of  these  the  most  characteristic  are  the 
following :  — 

228.  Columbic  Anhydride.   Cb2  05.  —  A  white  powder,  which 
becomes  crystalline  when  heated,  and  is  afterwards  insoluble  in 
all  acids.     It  has  a  Sp.  Gr.  between  4.37  and  4.53.     Before 
ignition,  and  when  in  condition  of  hydrate  (Columbic  Acid?), 
it  dissolves  in  strong  sulphuric  and  in  hydrofluoric  acids.    After 
boiling  with  strong  hydrochloric  acid,  in  which  it  is  nearly  in- 
soluble, the  product  dissolves  in  water,  and  the  solution  treated 
with  zinc  turns  blue  and  finally  deposits  a  blue-colored  oxide. 
When  a  large  excess  of  hydrochloric  acid  is  present,  the  solu- 
tion deposits  a  brown  oxide  under  the  same  conditions ;  but  the 
constitution  of  neither  of  these  compounds  is  as  yet  known.     It 
has  been  stated  that  oxides  having  the  composition  Cb202  and 
Cb204  have  also  been  obtained.       Columbic  acid  forms  salts 
called  columbates,  and,  besides  the  native  compounds  mentioned 
above,  we   are   acquainted   with  several  potassic  columbates, 
three  of  which  have  been  obtained  in  well-defined  crystals,  but 
they  have  a  very  complex  constitution. 

229.  Columbic   Chloride.     CbCl5.  —  A   yellow    crystalline 
solid,  melting  at  194°,  and  boiling  at  241°.     It  has  been  found 


§  232.]  TANTALUM.  297 

by  analysis  to  contain  65.28  per  cent  of  chlorine,  and  the  Qp. 
(J$£.  of  its  vapor,  by  experiment,  is  9.6. 

230.  ColumUc  Oxychloride.    Cb  0  C13 A  white  solid,  crys- 
tallizing in  silky  tufts,  which  volatilizes  in  the  air,  without  pre- 
viously melting,  at  400°.     It  contains,  according  to  analysis, 
48.9  per  cent  of  chlorine,  and  the  0p.  (£>r.  of  its  vapor  has  been 
found  to  be  7.9.     Moreover,  it  has  been  recently  proved  that  it 
contains  oxygen.       Both  chlorides,  when  treated  with  water, 
yield  columbic  acid. 

231.  Columbic  Oxy fluoride.    CbOF8. —  This  compound  is 
probably  formed  when  columbic  acid  is  dissolved  in  hydrofluoric 
acid,  but  it  has  not  yet  been  isolated  in  a  pure  condition.     The 
solution,  however,  forms  definite  crystalline  salts  with  several 
metallic  fluorides,  and  these  are  among  the  most  important  com- 
pounds of  columbium.     The  salt  2KF .  CbOF3.ff20  is  very 
readily  obtained  in  nacreous  scales,  and  being  far  more  soluble 
than  the  compound  of  tantalum  formed  under  the  same  condi- 
tions, 2KF.  TaF5,  it  gives  us  the  only  useful  means  yet  dis- 
covered of  separating  this  element  from  columbium.     A  salt 
has  also  been  formed,  having  the  composition  2KF .  CbF5,  and 
isomorphous  with  the  compound  of  tantalum  just  mentioned. 
It  is  interesting  as  pointing  to  a  fluoride  of  columbium,  CbF&1 
•which  is  not  otherwise  known. 

The  metal  columbium  has  not  with  certainty  been  obtained. 
The  black  powder  described  as  such  by  Rose  is  said  to  be  the 
oxide  Cb.202. 

An  infusion  of  gall-nuts  gives  with  acid  solutions  containing 
columbium  a  deep  orange-red  precipitate ;  and  by  this  reaction 
columbium  may  be  distinguished  from  tantalum,  which,  under 
the  same  conditions,  gives  a  bright  brown  precipitate. 

232.  TANTALUM.    7^  =  182.— This  element,  associated 
with  columbium  in  the  native  columbates  named  above,  is  the 
chief  constituent  of  Tantalite,  Yttrotantalite,  and  of  a  few  other 
minerals  equally  rare.     Tantalite  is  isomorphous  with  colum- 
bite,  has  the  same  composition,  save  only  that  the  acid  radical 
is  wholly  tantalum,  and  differs  chiefly  in  having  a  higher  Sp. 
Gr.,  which  varies  from  7  to  8.     Although  tantalum  is  so  closely 
allied  to  columbium,  yet  its  compounds  differ  from  those  of  this 
last  element  in  several  important  respects.     There  appears  to 
be  no  tendency  to  form  oxychlorides  or  oxyfluorides,  —  at  least 

13* 


298  QUESTIONS  AND  PROBLEMS.  [§232. 

no  such  compounds  are  known.  .  The  chloride  is  Ta  C75,  a  pale 
yellow  solid,  melting  at  211°,  boiling  at  242°,  and  having  a 
vapor  density  =  12.8.  It  contains  by  analysis  48.75  of  chlo- 
rine, and  is  decomposed  by  water,  yielding  tantalic  acid.  The 
fluoride,  is  in  like  manner,  Taffy.  It  forms  double  salts  with 
the  metallic  fluoride,  the  most  important  of  which  is  the  potassic 
fluotantalate,  2KF '.  TaF5,  mentioned  above.  Tantalic  anhy- 
dride, Ta205,  is  a  white  powder,  insoluble  in  acids.  It  closely 
resembles  colurnbic  anhydride,  and  is  prepared  in  a  similar  way 
from  the  native  tantalates,  but  it  has  a  higher  density  (Sp.  Gr. 
=  7.6  to  8),  arid  forms  with  the  alkalies  a  larger  number  of 
crystallized  salts.  There  is  a  hydrate  (Tautalic  Acid?),  and 
also  probably  several  lower  oxides  of  the  element.  A  solution 
of  1aCl5  in  strong  sulphuric  acid,  when  diluted  with  water  and 
reduced  with  zinc  becomes  colored  blue,  but  yields  no  brown 
oxide  as  in  the  case  of  columbium.  By  reducing  sodio-tantalic 
fluoride  with  sodium,  a  black  powder  is  obtained  which  has  been 
supposed  to  be  metallic  tantalum. 


Questions  and  Problems. 

1.  Calculate  the  percentage  composition  of  columbite,  on  the  as- 
sumption that  the  basic  radical  is  wholly  iron  and  the  acid  radical 
wholly  columbium.  Ans.  21.17  FeO  and  78.83  C\0y 

2.  Explain  the  meaning  of  the  symbol  of  columbite  in  (227). 

3.  How  far  do  the  theoretical  0«.  (Jfa.  of  columbic  chloride  and 
oxychloride  compare  with  the  experimental  results  ? 

4.  The  mean  of  twenty  analyses  of  the  potassio-columbic  oxyfluor- 
ide,  2KF.  CbOFs  .  HZO,  gave  the  following  results:  From  100  parts 
of  the  salt  there  were  obtained  by  the  process  of  analysis  adopted 
5.87  parts  of  water,  44.36  of  columbic  anhydride,  57.82  of  potassic 
sulphate,  and  31. 72  of  fluorine.     Assuming  that  the  symbol  of  colum- 
bic anhydride  is  C6205,  and  estimating  the  per  cent  of  oxygen  by  the 
loss,  deduce  the  percentage  composition  of  the  compound  and  its 
symbol. 

Ans.  Columbium,  31.12;  Potassium,  25.92;  Oxygen,  5.37;  Flu- 
orine, 31.72;  Water,  5.87. 

5.  What  would  be  the  atomic  weight  of  columbium  if  deduced 
from  the  result  of  the  above  analyses?  Ans.  93.9. 

6.  Previous  to  the  recent  investigations  of  Marignac,  the  symbol 


QUESTIONS  AND  PROBLEMS.  299 

of  columbic  acid  was  usually  written  CbOa  when  0  =  8,  or  Cb2Os 
when  0  =  16.  What  proofs  have  been  given  of  the  correctness  of 
the  symbol  adopted  in  this  book  ?  What  was  the  probable  cause  of 
the  error  made  by  the  earlier  investigators  ? 

7.  By  what  general  method  may  tantalum  be  separated  from  co- 
lumbium  ?     How  can  you  tell  when  the  separation  is  complete  ? 

8.  What  compounds  of  tantalum  and  columbium  are  isomorphous  ? 
What  bearing  does  this  fact  have  on  the  symbol  of  tantalic  anhy- 
dride ?     Does  the  vapor  density  of  tantalic  chloride  agree  with  the 
symbol  which  has  been  adopted  ?     Why  is  there  a  necessary  connec- 
tion between  the  symbol  of  the  chloride  and  that  of  the  anhydride  ? 

9.  How  may  tantalite  be  distinguished  from  columbite  ? 

10.  State  the  resemblances  and  the  differences  between  the  two 
members  of  this  group  of  elements. 


CHAPTER    XIX. 

THE  AETIAD  ELEMENTS. 

Division  I. 

233.  OXYGEN.   0=16.  —  Dyad.     The  most  abundant, 
and  the  most  widely  diffused  of  the  elements.     Forms  one  fifth 
of  the  atmosphere,  eight  ninths  of  water,  more  than  three  fourths 
of  organized  beings,  and  one  half  of  the  solid  crust  of  the  globe. 

234.  Oxygen  Gas.    0=0.  —  Exists  in  a  free  state  in  the  at- 
mosphere, but  mixed  with  nitrogen  gas.      May  be  extracted 
from  the  air  by  either  of  the  following  double  reactions.     Me- 
tallic mercury  or  baric  oxide  is  first  heated  in  the  air,  and  then 
the  products  of  the  first  reaction  raised  to  a  much  higher  tem- 
perature. 


2.  2ffO  =  2ff       ©=©.    2.  2Ba0= 


Generally  obtained  from  commercial  or  natural  products,  rich 
in  oxygen,  by  one  of  the  reactions  given  below.  The  materials 
must  in  each  case  be  heated  to  a  definite  temperature,  and  the 
last  two  reactions  require  a  full  red  heat. 

2KC103  =  2KCI  +  3  ©=©.!  [229] 


-f  8^0  +  3©=©.  [230] 
2Mn02  +  2ff2S04  =  2MnS04  -f  2ff20  +  ©=©.  [231] 
3Mn  02  =  Mn3  0±  +  ©=©.  [232] 

t  =  2ff20  +  2S02  +  ©=©.  [233] 


Also  by  electrolysis  of  water  and  by  [66].     Oxygen  gas  is  a 
chief  product  of  vegetable  life.      Under  the  influence  of  the 

1  This  reaction  is  greatly  facilitated  by  mixing  the  potassic  chlorate  with 
cupric  oxide  or  manganic  dioxide,  which,  however,  undergo  in  the  process 
no  apparent  change. 


§235.]  OXYGEN.  301 

sun's  rays  the  plants  decompose  the  carbonic  acid  of  their  food, 
fixing  the  carbon  and  liberating  the  oxygen.  Oxygen  gas  man- 
ifests intense  affinities,  but  these  are  only  called  into  play  under 
regulated  conditions.  (Review  Chapter  XII.  on  Combustion.) 
When  an  elementary  substance  unites  with  oxygen  it  is  said  to 
be  oxidized,  and  when  the  compound  is  decomposed  the  oxide  is 
said  to  be  reduced. 

235.  Oxygen  Compounds.  —  The  most  important  classes  of 
oxides  are  illustrated  by  the  following  symbols  and  examples: — 

i  ii 

1.  R20    or    R,R  0  as  in     H20        K20        Ag20s 

2.  R202    "    R,(R-0)*0       "        H202       K202       Ag20^ 

3.  RO      «     R-0  «        FeO        CaO       PbO, 

4.  R20     "     (R-R)--O  «        Cu20      HgzO      Pb20, 

5.  R02     «     (R-0)-~0  «        Mn02     Ba02      Pb02, 
m               v  in      m 

7.    R02     «    J?i<92  «        Sn02      Si02        C021 

IV  IV  IV 

II  &  IV  II  IV 

9.    R  0     "    R=0~[R~\=0     fi        Fe  0       Cr  0       Co  0 
v  v        v 

v  v  v 

1 1 .  R<> 0±    il     \R ~R)  1 04  V2  04        Sb2 04     -Bi2 0^ 

VI  VI 

12.  R03     «    RW3  "        S03        Se03      Mo03. 

As  a  rule,  the  oxides  of  the  forms  1  and  3  act  as  anhydride 
bases  (47),  and  are  called  protoxides.  On  the  other  hand,  the 
oxides  of  the  forms  6,  7,  10,  and  12  generally  act  as  anhydride 
acids.  The  oxides  of  the  form  8  are  called  sesquioxide.  They 
usually  act  as  basic,  but  sometimes  as  acid  anhydrides,  and  at 
other  times  like  the  hyperoxides  mentioned  below.  The  oxides 
of  the  forms  9  and  11  are  very  indifferent  bodies,  and  those  of 
the  first  class  are  sometimes  called  saline  oxides.  The  oxides 
of  the  forms  2  and  5  are  called  di  or  hyper-oxides.  They  act 
as  powerful  oxidizing  agents,  readily  giving  up  one  half  of  the 
oxygen  they  contain  [74]  [77].  The  oxides  of  the  form  4  are 
called  suboxides.  They  sometimes  act  as  anhydride  bases,  but 
in  most  cases  when  acted  on  by  acids  they  change  into  protox- 


302  OXYGEN.  [§236. 

ides,  either  giving  up  one  half  of  the  metal  or  taking  up  as  much 
again  oxygen  as  they  contain.  The  relation  of  the  oxides  to 
the  acids,  bases,  and  salts  has  been  already  explained.  (Review 
Chapters  IX.  and  X.) 

Besides  the  above  classes  of  oxides,  all  of  which  comprise 
actual  compounds,  there  are  others,  most  of  which  are  only 
known  as  compound  radicals.  With  many  of  these  radicals  the 
student  is  already  familiar,  such  as  S02,  SO,  NOZ,  NO,  PO,  in 
all  of  which  the  oxygen  atoms  only  satisfy  a  part  of  the  affini- 
ties of  the  multivalent  atoms,  with  which  they  are  grouped,  and 
the  quantivalence  of  the  radical  is  easily  found  by  Wurz's  rule. 
(28.)  The  chemists  have  also  been  led  to  assume  a  very  differ- 
ent type  of  oxygen  radicals,  in  which  the  affinities  of  the  oxygen 
atoms  predominate,  and,  moreover,  it  is  frequently  convenient, 
in  expressing  the  composition  of  complex  compounds,  to  indicate 
these  radicals  by  a  single  symbol.  The  following  examples 
illustrate  the  most  important  classes  of  these  radicals :  — 

Radicals.  Symbols.  Examples. 

RO          (R-6)  Ro  Ho        Ko         (NJB^o. 

R02         (0-R-O)  Ro  Oao       Zno        Feo. 

VI  VI  VI 


It  will  be  noticed  that  the  number  of  oxygen  atoms  in  all 
these  cases  corresponds  to  the  quantivalence  of  the  metallic  ele- 
ment with  which  they  are  united,  and  that  the  quantivalence  of 
the  radical  is  the  same  as  that  of  its  characteristic  element. 
Hydroxyl,  Ho,  is  the  type  of  this  class  of  radicals,  and  names 
may  be  given  to  them  all  formed  after  the  same  analogy  as 
Potassoxyl,  Zincoxyl,  —  but  such  names  are  rarely  used.  The 
relations  of  this  type  of  radicals  to  the  three  great  classes  of 
chemical  compounds  has  been  already  in  part  illustrated  (108), 
and  will  be  still  further  developed  in  the  present  chapter. 

236.  Ozone.  (0-0)  =  0.  —  The* best  opinion  that  can  at  pres- 
ent be  formed  in  regard  to  the  constitution  of  this  remarkable 
substance  is  expressed  by  the  rational  symbol  here  given. 
Ozone  is  formed  under  a  great  variety  of  conditions,  as,  —  1. 
During  the  passage  of  electric  sparks  through  air  or  oxygen. 
2.  During  the  electrolysis  of  water.  3.  During  the  slow  com- 


§  23G.]  OXYGEN.  303 

bustion  of  phosphorus  in  moist  air.  4.  During  the  slow  com- 
bustion of  alcohol,  ether,' and  volatile  oils.  5.  By  decomposing 
potassic  permanganate  with  sulphuric  acid,  and  by  several  other 
similar  reactions.  Ozone  as  thus  obtained,  however,  is  very 
largely  diluted  with  air  or  oxygen  gas,  and  we  have  not  yet 
succeeded  in  preparing  it  in  a  pure  condition.  It  differs  from 
ordinary  oxygen  gas,  —  1.  In  having  a  peculiar  odor,  with  which 
we  are  familiar,  as  a  concomitant  of  electrical  action.  2.  In 
acting  as  a  powerful  oxidizing  agent  at  the  ordinary  temper- 
ature of  the  air.  It  corrodes  cork,  india-rubber,  and  other  or- 
ganic materials.  It  bleaches  indigo.  It  even  oxidizes  silver, 
and  displaces  iodine  from  its  metallic  compounds.  If  a  slip  of 
paper  moistened  with  starch  and  potassic  iodide  is  inserted  in 
a  jar  containing  the  smallest  trace  of  ozone,  it  is  immediately 
colored  blue,  owing  to  the  liberation  of  the  iodine  (119).  In 
like  manner,  paper  wet  with  a  solution  of  manganous  sulphate 
is  turned  brown  by  ozone,  owing  to  the  oxidation  of  the  man- 
ganese, and  paper  stained  with  plumbic  sulphide  is  bleached  by 
the  same  agent,  because  the  black  sulphide  is  changed  to  the 
white  sulphate.  3.  In  the  fact  that  its  Sp.  Gr.  is  24  instead  of 
16.  The  formation  of  ozone  in  a  confined  mass  of  oxygen  gas 
is  attended  with  a  reduction  of  volume ;  and  since  the  ozone  thus 
formed  may  be  absorbed  by  oil  of  turpentine,  we  have  thus  the 
means  of  determining  its  specific  gravity,  and  the  results,  if  cor- 
rect, prove  that  the  molecule  of  ozone  consists  of  three  oxygen 
atoms.  Again,  during  most  cases  of  oxidation  by  ozone,  the 
volume  of  the  ozonized  oxygen  does  not  change,  and  this  fact  is 
consistent  with  the  theory  of  its  constitution  which  our  molecular 
formula  expresses,  as  is  illustrated  by  the  following  reaction :  — 

Ag-Ag  +  2(OO)  =  0  =  Ag202  +  20=0.       [234] 

li  has  been  shown,  however,  that  oil  of  turpentine  absorbs 
the  molecule  of  ozone  as  a  whole,  and  is,  therefore,  an  exception 
to  the  general  rule.  The  metal  in  the  above  reaction  is  raised 
to  the  condition  of  peroxide,  and  it  is  probable  that  several  of 
the  oxides  and  oxygen  acids  contain  one  or  more  atoms  of  oxy- 
gen in  the  same  condition  as  in  ozone.  Such  compounds  have 
been  called  ozonides,  and  among  them  are  classed  the  peroxides 
of  silver,  lead,  and  manganese,  the  sesquioxides  of  nickel  and 


304  OXYGEN.  [§237. 

cobalt,  as  also  chromic,  manganic,  and  permanganic  acids,  with 
their  various  salts.  Ozone  appears  to  be  constantly  present  in 
the  atmosphere,  and  important  effects  have  been  attributed  to 
its  influence.  It  has  been  thought  to  be  the  active  agent  in  all 
processes  of  slow  combustion  and  decay,  and  to  play  an  impor- 
tant part  in  the  economy  of  nature.  At  a  temperature  of  300° 
ozone  is  instantly  changed  into  common  oxygen  gas,  and  at  a 
temperature  no  higher  than  boiling  water,  it  slowly  returns  to 

the  same  condition. 

+ 

237.  Antozone.  (0-0)  =  0.  —  Whenever  ozone  is  prepared, 
there  appears  to  be  formed  at  the  same  time  a  second  modifica- 
tion of  oxygen  gas,  which  presents  such  a  singular  antithesis  to 
ozone  as  to  lead  us  to  believe  that  it  is  in  fact  the  same  sub- 
stance, only  oppositely  polarized.  Hence  we  have  called  it  an- 
tozone,  and  assigned  to  it  the  symbol  at  the  head  of  this  section, 
although  our  theory  is  not  based  on  any  conclusive  experiments, 
and  our  knowledge  of  the  substance  is  still  very  imperfect.  It 
may  be  obtained  in  several  ways,  —  1.  When  dry  electrified  air 
is  passed  through  a  solution  of  pyrogallic  acid  or  potassic  iodide, 
the  ozone  is  absorbed  and  the  air  is  left  charged  with  antozone. 
2.  When  baric  peroxide  is  dropped  into  sulphuric  acid,  the  oxy- 
gen evolved  is  more  or  less  charged  with  the  same  agent.  3. 
When  phosphorus  is  burnt  in  dry  air,  a  small  amount  of  oxygen 
is  always  left  unconsumed,  and  this  appears  to  be  in  th£  condi- 
tion of  antozone.  Indeed,  it  has  been  supposed  that,  in  all  sim- 
ilar processes  of  oxidation,  both  ozone  and  antozone  are  formed ; 
but  that,  while  the  oxygen  atoms  of  the  first  enter  into  combi- 
nation with  the  burning  body,  those  of  the  last  do  not,  owing  to 
their  polar  condition. 

Antozone  has  an  odor  like  ozone,  but  much  more  repulsive. 
It  does  not  displace  iodine  or  color  the  iodized  paper.  It  does 
not  oxidize  silver  or  the  solution  of  manganous  sulphate,  but,  on 
the  contrary,  removes  from  the  paper  prepared  with  the  man- 
ganous salt  the  brown  stain  which  ozone  had  made.  On  all 
ozonides  it  acts  as  a  reducing  agent.  [236.]  There  is,  how- 
ever, another  class  of  substances  which  it  oxidizes,  and  ^jnong 
these  the  most  important  is  water,  with  which  it  forms  hydric 
peroxide. 

0+  0-0.         [235] 


§237.]  QUESTIONS  AND  PROBLEMS.  305 

In  many  processes  of  ozonizing  air,  the  antozone  unites  with 
and  thus  condenses  the  vapor  present,  although,  in  most  cases 
at  least,  the  union  appears  to  be  rather  mechanical  than  chemi- 
cal. The  reaction  is  consequently  attended  with  the  formation 
of  mists  or  clouds,  which  is  one  of  the  most  striking  properties 
of  antozone.  The  smoke  of  gunpowder,  tobacco,  and  smoulder- 
ing wood  has  been  thought  to  be  an  antozone  cloud,  and  the 
clouding  of  gas  jars  in  many  chemical  experiments  has  been 
referred  to  the  same  cause.  Opposed  to  the  ozonides  we  have 
a  class  of  antozonides,  among  which  have  been  classed,  besides 
the  peroxide  of  hydrogen,  the  peroxides  of  barium,  strontium, 
sodium,  and  potassium,  and  reactions  may  be  obtained  between 
these  two  classes  of  compounds  which  are  very  interesting. 
They  mutually  decompose  each  other,  with  the  evolution  of 
oxygen  gas,  thus :  — 

(Pb-0)-d  +  ffJffo=0  =  PbO-\-ff20  +  0-0.  [236] 

Compare  also  [75].  Antozone  is  more  unstable  than  ozone, 
and  changes  back  to  oxygen  gas  at  a  still  less  elevation  of  tem- 
perature. 


Questions  and  Problems. 

1.  Wbat  is  the  reason  for  writing  the  symbol  of  oxygen  gas  O=0? 
(17)  and  (19.) 

2.  What  is  the  difference  between  the  condition  of  oxygen  gas  in 
the  atmosphere,  and  that  of  the  same  gas  in  a  pure  condition  con- 
tained in  a  bell-glass  standing  over  a  pneumatic  trough  ? 

3.  Were  the  nitrogen  gas  of  the  atmosphere  removed,  would  the 
physical  condition  of  the  oxygen  gas  be  changed  ? 

4.  If  by  either  of  the  methods  [228]  oxygen  gas  is  obtained  di- 
rectly from  the  atmosphere,  how  many  litres  of  air  would  be  required 
to  yield  one   litre  of  oxygen  gas  at  same  temperature  and  press- 
ure?    (59.)  Ans.  4.77  litres  of  air. 

5.  How  much  potassic  chlorate  must  be  used  to  yield  100  litres  of 
oxygen  gas  at  30°  and  38  c.  m.  pressure?  Ans.  165  grs. 

6.  What  weight  of  potassic  dichromate   [230]  must  be  used  to 
yield  a  litre  of  oxygen  gas,  Sp.  Gr.  =  96  ?  Ans.  52.77  grs. 

7.  If  32.05  grammes  jof  potassic  chlorate  are  decomposed  in  a 


306          QUESTIONS  AND  PROBLEMS. 

closed  vacuous  vessel  of  1,010  cTmT8  capacity,  what  will  be  the  tension 
of  the  gas  in  the  vessel  at  273°  ?         Ans.  131.6  c.  m. 

8.  What  weight  of  oxygen  gas  is  required  to  fill  a  globe  of  10  litres' 
capacity  at  27°. 3  and  38  c.  m.  pressure?  Ans.  6.515  gram. 

9.  From  a  given  weight  of  Mn02  how  much  more  oxygen  gas  can 
be  obtained  by  reaction  [231]  than  by  [232]  ?  Ans.  \  more. 

10.  A  volume  of  air  measuring  100  c.  niT8  is  mixed  with  50  c.  m.8 
of  hydrogen  gas  and  exploded.     What  volume  of  gas  is  left,  assum- 
ing that  the  volumes  are  all  measured  under  standard  conditions,  and 
that  all  the  water  formed  is  condensed  ?     (59.) 

Ans.  87.12  cTm:8. 

11.  In  an  experiment  like  the  last,  with  the  same  initial  volume 
of  air  and  hydrogen,  the  volume  of  the  residual  gas  measured  89.41 
c.  m.8    What  is  the  composition  of  the  air  ?     It  is  assumed  that  the 
volumes  are  measured  under  a  constant  pressure  of  76  c.  m.,  and  at 
a  temperature  at  which  the  tension  of  aqueous  vapor  equals  2  c.  m. 

Ans.  20.96  oxygen,  79.04  nitrogen. 

12.  Analyze  reaction  [230],  and  show  from  which  of  the  factors 
the  oxygen  is  derived. 

13.  Represent  reaction  [232]  by  graphic  symbols. 

14.  What  volume  of  chlorine  gas  is  required  to  decompose  one 
litre  of  aqueous  vapor  ?  Ans.  1  litre. 

15.  If  one  gramme  of  water  is  decomposed  by  galvanism  in  a 
closed  glass  globe  containing  1.86  litres  of  air  under  normal  condi- 
tions, what  will  be  the  tension  of  the  resulting  gas  mixture,  leaving 
out  of  the  account  the  tension  of  the  aqueous  vapor  which  may  be 
present?  Ans.  152  c.  m. 

16.  Represent  by  graphic  symbols  the  constitution  of  the  various 
classes  of  oxides  and  oxygen  radicals. 

17.  In  the  symbols  of  acids,  hydrates,  and  salts  (35)  written  on 
the  water  type,  to  what  do  the  oxygen  radicals  correspond  ? 

18.  Explain  the  change  of  color  which  takes  place  when  paper 
moistened  with  a  solution  of  starch  and  potassic  iodide  is  exposed  to 
the  action  of  ozone. 

1 9.  Explain  the  method  of  finding  the  Sp.  Gr.  of  ozone. 

20.  Can  you  devise  a  method  of  finding  the  Sp.  Gr.  of  ozone 
based  on  the  principle  of  (58)  ? 

21.  Explain  the  reasons  for  writing  the  symbol  of  ozone  (#-#)=#. 


QUESTIONS  AND  PROBLEMS.  307 

22.  How  would  you  write  the  symbols  of  argentic  peroxide  and 
plumbic  peroxide,  on  the  same  principle  ? 

23.  Why  is  it  essential  in  preparing  antozone  that  the  electrified 
air  should  be  dry  ? 

24.  In  what  different  ways  may  the  symbol  of  hydric  peroxide  be 
written,  and  what  theories  of  its  composition  do  the  symbols  suggest? 
By  what  reactions  are  these  theories  sustained  ? 


308  SULPHUR.  [§  238. 


Division  U. 

238.  SULPHUR.  S  =  32.  —  Usually  bivalent  when  in 
combination  with  metals  or  positive  radicals,  but  in  other  asso- 
ciations frequently  quadrivalent  and  sexivalent.  Widely  and 
abundantly  distributed  in  nature,  chiefly  in  combination,  form- 
ing various  metallic  sulphides  and  sulphates.  The  most  abun- 
dant of  these  are  iron  pyrites,  FeS*  and  gypsum,  CaSO^ .  2ff20. 
Found  also  native  in  volcanic  districts.  It  is,  moreover,  an  es- 
sential, although  a  very  subordinate,  ingredient  of  the  animal 
tissues.  Sulphur  is  very  closely  allied  to  oxygen,  and,  corre- 
sponding to  each  metallic  oxide,  there  is  usually  a  sulphide  of 
the  same  form  ;  and,  substituting  the  symbol  of  sulphur  for  that 
of  oxygen,  the  table  of  oxides  on  page  301  will  serve  equally 
well  as  a  classification  of  the  sulphides.  Moreover,  we  have 
found  it  convenient  to  assume  a  number  of  sulphur  radicals  cor- 
responding in  all  respects  to  the  oxygen  radicals,  and  we  repre- 
sent them  by  separate  symbols  formed  in  a  similar  way.  Thus, 

Jfi,  Pbs,  Cutf,  Sbtf  stand  for  the  radicals  HS,  PbS2,  Cu2S^ 
Sb2S6  respectively. 

The  greater  part  of  the  sulphur  of  commerce  comes  from  the 
mines  of  Sicily,  where  it  is  either  melted  or  distilled  from  the 
volcanic  earth.  A  small  quantity  is  obtained  by  roasting  or 
distilling  iron  pyrites.  Common  sulphur  is  a  very  brittle,  yel- 
low solid,  melting  at  114°,  and  boiling  at  440°,  when  it  forms  a 
dense  red  vapor.  It  is  insoluble  in  water,  and  nearly  so  in 
alcohol,  ether,  and  chloroform,  but  readily  soluble  in  carbonic 
bisulphide,  benzole,  and  oil  of  turpentine,  the  solvent  power  of 
the  last  two  liquids  being  greatly  increased  by  heat.  Sulphur 
assumes  a  great  variety  of  allotropic  modifications,  which  are 
manifested  by  differences  of  crystalline  form,  specific  gravity, 
solubility,  and  color.  At  the  ordinary  temperature  it  crystal- 
lizes in  octahedrons  of  the  orthorhombic  system,  Sp.  Gr.  2.05, 
and  above  105°  in  oblique  prisms  of  the  monoclinic  systems,  Sp. 
Gr.  1.98.  Moreover,  the  one  crystalline  condition  passes  into 
the  other  at  the  temperature  at  which  it  is  normally  formed. 
If  heated  to  230°,  melted  sulphur  becomes  darker  colored,  thick, 
and  pasty,  and  if  suddenly  cooled  the  mass  remains  plastic  for 


§  239.]  SULPHUR.  309 

some  time.  At  100°  this  plastic  material  suddenly  changes  back 
to  brittle  sulphur,  with  evolution  of  heat,  and  the  same  change 
soon  follows,  although  more  slowly,  at  the  ordinary  temperature. 
If  sulphur  is  heated  to  230°,  and  suddenly  cooled  several  times 
in  succession,  it  is  in  part  converted  into  a  peculiar  dark-colored 
variety,  wholly  insoluble  in  all  solvents,  and  easily  separated 
by  carbonic  sulphide  from  the  unchanged  portion.  Moreover, 
ordinary  flowers  of  sulphur  (formed  by  condensing  the  vapor 
of  sulphur  in  cold  brick  chambers)  consist  in  part  of  a  yellow 
powder,  insoluble  in  carbonic  sulphide,  which  appears  to  be  still 
another  condition  of  sulphur,  and  several  other  modifications, 
including  a  black  and  a  red  variety,  have  been  described  as 
distinct  allotropic  states.  Some  chemists  have  thought  to  find 
among  these  various  modifications  a  difference  of  polar  condition 
similar  to  that  observed  in  the  modifications  of  oxygen.  Sul- 
phur appears,  even  in  the  state  of  vapor,  to  present  differences 
of  condition.  Just  above  its  boiling  point  the  Sp.  Gr.  of  sul- 
phur vapor  is  96,  which  corresponds  to  the  molecular  formula 
S^S3',  and  not  until  the  temperature  reaches  1,000°  does  the 
Sp.  Gr.  become  32,  corresponding  to  the  formula  S=S,  like  that 
of  oxygen  gas.  Sulphur  has  strong  affinities  for  the  metals, 
many  of  which  burn  in  its  vapor  with  great  brilliancy.  It  has 
also  a  strong  affinity  for  oxygen.  It  is  very  combustible,  taking 
fire  at  a  low  temperature,  and  forming  by  burning  S02.  It  is 
chiefly  used  for  making  sulphuric  acid,  and  vulcanizing  india- 
rubber;  but  it  has  many  subordinate  applications  both  in  the 
arts  and  in  medicine.  The  so-called  milk  of  sulphur,  used  in 
pharmacy,  is  obtained  by  dissolving  flowers  of  sulphur  in  alka- 
line liquids,  and  subsequently  precipitating  with  acid. 

239.  Hydric  Sulphide,  Sulphohydric  Acid,  Sulphuretted 
Hydrogen,  ff.2S.  —  A  colorless  gas,  which  by  pressure  and  cold 
may  be  condensed  to  a  limpid,  colorless  liquid  (Sp.  Gr.  =  0.9), 
boiling  at  — 62°,  and  freezing  at  — 86°.  Is  soluble  in  water 
and  alcohol,  one  measure  of  water  at  0°  dissolving  4.37  meas- 
ures, and  one  volume  of  alcohol  dissolving  17.9  measures,  of  the 
gas  at  the  same  temperature.  Has  a  repulsive  odor,  and  is  a 
constant  product  of  decaying  animal  tissues.  Generally  obtained 
by  the  reaction 

FeS  +  (H2S04  +  Aq)  =  (FeSO,  +  Aq)  +  H,S;  [237] 


310  SULPHUE.  [§239. 

but  as  the  ferrous  sulphide  commonly  used  contains  more  or  less 
metallic  iron,  the  gas  thus  prepared  is  mixed  with  hydrogen. 
It  is  obtained  in  a  purer  condition  from 

Sb2S3  +  (QHCl  +  Aq)  =  (2SbCl3  -f-  Aq)  +  3ff2S.  [238] 

Hydric  sulphide  is  very  combustible,  and  burns  with  a  pale 
blue  flame. 

=  2ff20  +  2S02.  [239] 


The  solution  of  the  gas  exposed  to  the  air  soon  becomes  turbid, 
owing  to  the  oxidation  of  the  hydrogen  and  consequent  sepa- 
ration of  sulphur. 


Aq)  +  ©=©  =  (2ff20  +  Aq)  +  S=S.  [240] 

If  the  action  is  assisted  by  porous  solids,  the  oxidation  is  more 
complete. 


(H2S  +  Aq)  +  2©=©  =  (HfOfSOs  +  Aq).  [241] 

The  substance  is  also  decomposed  by  chlorine,  bromine,  or 
iodine. 


(2H2S  +  27-7+  Aq)  =  (4777+  Aq)  +  &&.  [242] 

On  this  last  reaction  is  based  a  simple  process  of  determining 
volumetrically  the  amount  of  H2S  in  a  given  solution.  The 
compound  may  be  analyzed  by  heating  metallic  tin  in  a  confined 
volume  of  the  gas. 

SI^  +  Sn  —  SnS  +  SHS.  [243] 

Although  the  sulphur  is  removed  by  the  tin,  the  volume  of  the 
gas  does  not  change.  Hydric  sulphide  is  not  unfrequently 
formed  in  nature  from  calcic  sulphate,  which  in  contact  with 
decaying  animal  or  vegetable  matter  loses  its  oxygen,  when 
the  carbonic  acid  of  the  atmosphere,  acting  on  the  resulting 
calcic  sulphide,  sets  free  the  compound  in  question.  It  is  thus 
that  the  soluble  sulphides  in  many  mineral  springs  probably 
originate. 

Hydric  sulphide  is  one  of  the  most  important  chemical  re- 
agents, and  is  used  to  convert  into  sulphides  various  metallic 
hydrates  and  other  salts. 


§239.]  SULPHUR.  311 

1.  Action  on  alkaline  hydrates. 

(K-0-JI+  H2S  +  Aq)  =  (K-S-ff+  ff20  +  Aq).  [244] 

(K-S-JI+  K-0-H+  Aq)  =  (K2S+ff20  +  Aq).  [245] 

Thus  may  also  be  formed  Na-Hs,  Na?S,  Nfffffs, 


(38.) 

2.  Action  on  salts  of  the  more  electro-negative  metals. 

(CdSO,  +  H2S  +  Aq)  =  CdS  +  (&2S04  +  Aq).  [246] 
So  also  may  be  precipitated  from  acid  solutions  of  their  salts 


As2S3,      Sb2S3,       Sb2S5,       SnS,       SnS»       PtS2,       Au4S4, 

Yellow.  Red.  Orange.  Brown.  Yellow.  Brown.  Black. 

all  of  which  are  soluble  in  alkaline  sulphides,  and 

CdS,       CuS,       Bit/8*      Ag2S,        HgS,       [Eg  AS,       PbS, 

Yellow.  Black.  Black.  Black.  Black.  Black.  Black. 

all  of  which  are  insoluble  in  alkaline  sulphides. 

3.  Action  on  salts  of  the  more  electro-positive  metals.     The 
following  sulphides,  although  not  precipitated  from  acid  solu- 
tions, are  precipitated  when  sufficient  ammonia  is  added  to  neu- 
tralize all  the  acids  present,  or  when  an  alkaline  sulphide  is 
used  in  place  of  H2S. 

ZnS,  MnS,  FeS,  NiS,  OoS. 

TVhite.  Pink.  Black.  Black.  Black. 

At  the  same  time  aluminum  and  chromium  are  also  precipitated 
as  hydrates.  The  remaining  common  metals,  viz.  :  Ha,  Sr,  Ca, 
Mg,  K,  and  Na,  forming  sulphides  soluble  in  water,  are  not  pre- 
cipitated by  H2S  under  any  conditions.  Thus  ff2S  serves  to 
divide  the  metallic  radicals  into  groups,  and  on  these  relations 
the  ordinary  methods  of  qualitative  analysis  are  based. 

4.  Action  as  reducing  agent. 


Ck  +  ZffCl  +  Aq)  +  S.  [247] 

(Kz[  Crz~]  07  +  SffCl 
d> 


Green. 


+  2KCI  +7ff20  +  Aq)  +  S»  [248] 


Q.    [249] 

Pentathlonlo  Acid. 


312  SULPHUR.  [§240. 


240.  Hydric  Persulphide,  H^S^  analogous  to  H^O^  can  be 
obtained  by  gradually  adding  to  hydrochloric  acid  sodic  bisul- 
phide.    It  is  a  yellow,  oily  liquid,  and  very  unstable. 

241.  Alkaline  Sulphides  and  Sulphohydrates.  —  Solutions  of 
the  simple  sulphides  and  sulphohydrates  are  best  formed  as 
above.     These  solutions  readily  dissolve  sulphur,  and  various 
persulphides  are  thus  formed.     The  following  six  sulphides  of 
potassium  are  known  :  K2S,  K2S2,  K2S&  KZS^  K2S5,  and  KZS7. 
Other  modes  of  preparing  similar  compounds  are  illustrated  by 
the  following  reactions  :  — 


[250] 

Ignited  in  gas  current. 

125+  (6JT-  0-ff+  Aq)  = 

Boiled  in  solution.         ^^  +  ^  Q  +  ^  Q  +  ^    ^^ 

Fentasulphide.    Hyposulphite. 


.  [252] 

Melted  together  at  a  high  temperature. 

SS  +  3K2=02=00  =  2K2S3  +  K2S20,  +  3  CO*  or 


125+  3K2=02=CO  =  2K2S5  +  K2S20S  +  3(702. 

Melted  together  at  a  lower  temperature. 

The  products  of  the  last  two  reactions  are  not  constant,  but 
various  persulphides  are  formed,  depending  on  the  temperature 
and  the  conditions  of  the  process.  The  resulting  mixture  is  a 
yellow  solid  called  liver  of  sulphur.  When  treated  with  acids, 
the  various  sulphides  react  as  follows  :  — 

(K-Hs  +  HCl  +  Aq)  =  (KCl  +  Aq)  +  3SA  [254] 

(K2S  +  2HCI  +  Aq)  =  (2KCI  +  Aq)  +  SJA  [255] 

(K2S3  +  2HCI  +  Aq)  =  (2  KCl  +  Aq)  +  S2  +  IHA  [256] 


3  +  SffCl  +  Jy)  = 
S02  +  JET,0  +  Aq)  +  9S  +  2HI2^.  [257] 


Solutions  of  the  alkaline  sulphides  or  sulphohydrates  absorb 
oxygen  from  the  air,  and  are  thus  changed  into  persulphides 
and  hyposulphites. 

(SNff4-S-ff+  Aq)  +  5©=©  = 

Colorless  solution. 


§243.]  SULPHUR.  313 

Sulphur  and  hydric  sulphide  react  on  the  alkaline  earths  in 
nearly  the  same  ways  as  on  the  alkalies. 

Ca  0  +  H,S  =  CaS  +  ff2  0.  [259] 

Ignited  in  gas  current. 


CaS04  +  ±ff-ff=  CaS  +  ±H20.  [260] 

Ignited  in  gas  current. 

CaS  0^  +  4(7=  CaS  +  ±CO.  [261] 

Ignited  together. 

2  CaS  +  HfOz=Hz  =  Ca=S2=ff2  +  Ca-OfH^     [262] 

Mixed  with  water. 

(Ca=O2=H2  +  2ff2S+Aq)  = 

Pa^ng^Sthroughmilkoflime.        ^  Ca=S2=ff2  +  2ff20-}-Aq).    [263] 


By  boiling  sulphur  with  milk  of  lime,  a  mixture  of  calcic  hy- 
posulphite with  various  calcic  persulphides  is  obtained,  among 
which  may  be  distinguished  CaS2  and  CaS6.  By  melting  to- 
gether sulphur  and  calcic  hydrate  or  carbonate,  there  results  a 
mixture  of  calcic  sulphide  and  calcic  sulphate.  If  pulverized 
charcoal  is  also  added,  the  product  is  chiefly  calcic  sulphide. 

242.  Compounds  of  Sulphur  and  Oxygen.  —  The  following 
are  known  :  — 

Sulphurous  Anhydride  SO&  9 

Sulphurous  Acid  HfOz=SO, 

Hyposulphurous  Acid  Hf  02=(S-  0-S), 

Sulphuric  Anhydride  £03, 

Sulphuric  Acid  ff2=OfS02, 

Nordhausen  Acid  Hf  02=(S02-  0-S02), 

Dithionic  Acid  Hz=  02=(S02-S02), 

Trithionic  Acid  Sf 

Tetrathionic  Acid  Hf 

Pentathionic  Acid  Jf2=  02=(S02-S-S-S~S02). 

243.  Sulphurous  Anhydride.  S02.  —  Colorless  gas,  having 
a  familiar  suffocating  odor.     It  is  easily  condensed  to  a  colorless 
liquid,  boiling  at  —  10°  and  freezing  at  —  76°  ;  0|).  <&r.  =  1.49. 
Natural  product  of  volcanic  action,  and  abundantly  evolved  dur- 
ing the  roasting  of  copper  pyrites  and  other  sulphurous  ores. 
May  be  prepared  by  either  of  the  following  reactions  :  — 

14 


314  SULPHUR.  [§244. 

[264] 


Burning. 

2H2S04  +  ffff  =  HgSOt  +  2^0  +  ^©2.  [265] 

2Jf2S04  -f  O=  2^©2  -|-  O©a  -f2IH2(o).  [266] 

S=S  +  Jtfw  02  =  JfnS  +  ^©2.  [267] 
May  be  decomposed  by  the  reactions 

2S02  +  ±ff-ff=  ±ff20  +  S-S.  [268] 

SO,  +  3ff-ff=:  2ff20  +  ff2S.  [269] 

The  first  reaction  is  obtained  by  passing  a  mixture  of  the  two 
gases  through  a  red-hot  tube  ;  the  second,  by  adding  to  the  so- 
lution containing  S02&  small  amount  of  hydrochloric  acid  with 
a  few  pieces  of  zinc.  The  ^/S  may  be  detected  by  a  strip  of 
paper  moistened  with  a  solution  of  acetate  of  lead,  and  the  reac- 
tion gives  us  the  means  of  discovering  small  quantities  of  SOZ. 
Sulphurous  anhydride  is  a  powerful  reducing  agent.  Thus 


5S02  +  4#20  +  Aq)  = 

(I-I+  5H2S04  +  Aq).  [270] 


(As205  +  2S02  +  2#20  +  Aq)  = 

(As203  +  2ff2S04  +  Aq).  [271] 


[272] 

(2S02  +  2#26>  +  Aq)  +  ©=©  ==  (2ff2S04  +  Aq).  [273] 
Pb02  +  ^©2  =  PtoS04.  [274] 


It  is  also  a  powerful  disinfecting  and  antiseptic  agent,  and  is 
much  used  for  retarding  fermentation  and  putrefaction.  It  also 
bleaches  some  of  the  more  fugitive  colors,  but  the  effect  is  fre- 
quently transient,  and  the  reaction  not  well  understood. 

244.  Sulphites.  —  At  0°  water  absorbs  68.8  times  its  bulk  of 
SO&  and  three  crystalline  hydrates  have  been  described,  one  of 
which  has  the  composition  S02  .  If20,  and  has  been  regarded  as 
sulphurous  acid,  but  this  opinion  may  be  questioned.  The  aque- 
ous solution  acts  in  all  .its  mechanical  relations  like  the  simple 


§246.]  SULPHUR.  315 

solution  of  a  gas.  Nevertheless,  in  its  chemical  relations  it  acts 
like  an  acid,  and  yields,  with  many  of  the  metallic  oxides,  hy- 
drates, or  carbonates,  a  numerous  class  of  salts  called  the  sul- 
phites. The  following  examples  will  illustrate  their  general 
composition :  — 

Hydro-sodic  Sulphite  HJfa = Of  SO .  4ff2  0, 

Disodic  Sulphite  No?  Of  SO .  7ff2  0, 

Calcic  Sulphite  Oa  =  Of  SO. 

The  sulphites  are  generally  best  prepared  by  transmitting  a 
stream  of  S02  through  water  in  which  the  metallic  oxide,  hy- 
drate, or  carbonate  is  suspended.  The  alkaline  salts  are  the 
only  sulphites  which  are  freely  soluble  in  wa^r.  The  sulphites 
of  barium,  strontium,  and  calcium  dissolve  to  some  extent  in 
water  charged  with  SO^  and  in  this  respect  the  sulphites  re- 
semble the  carbonates.  Argentic  sulphite,  which  may  be  read- 
ily obtained  by  precipitation,  undergoes  a  remarkable  reaction 
when  boiled  with  water. 

AffOfSO  +  (H20  +  Aq)  = 

Ag-Ag  +  (ff2=02=SO2  +  Aq).  [275] 

245.  Hyposulphites.  —  Hyposulphurous  acid  has  never  been 
isolated ;  but  several  hyposulphites  may  be  obtained  by  passing 
a  stream  of  SOZ  through  solutions  of  the  corresponding  sul- 
phides, or  digesting  a  solution  of  the  sulphite  on  powdered 
sulphur. 

S  +  (Na2=02=SO  +  Aq)  =  (NafOf(S-0'S)  +  Aq.  [276] 

Calcic  hyposulphite  is  formed  spontaneously  in  large  quanti- 
ties, both  in  the  refuse  lime  taken  from  the  purifiers  of  the  gas- 
works, and  in  the  refuse  after  the  lixiviation  of  the  black-ball  at 
the  alkali  works,  and  from  this  source  sodic  hyposulphite  is 
now  obtained.  It  is  the  only  hyposulphite  of  practical  value, 
and  is  not  only  used  in  photography,  but  also  for  removing  the. 
last  traces  of  chlorine  from  the  bleached  pulp  used  in  paper- 
making,  and  in  the  treatment  of  silver  ores. 

246.  Sulphuric  Anhydride.  S03.  —  Soft,  white,  silky-looking 
crystalline  solid,  melting  at  25°,  and  volatilizing  at  35°.     May 
be  obtained  either  by  distillation  from  the  Nordhausen  acid  or 


316  SULPHUR.  [§247. 

from  sodic  disulphate,  or  else  by  passing  a  mixture  of  S02  and 
0=0  through  a  heated  tube  filled  with  platinum  sponge. 


[277] 

=  Na2=O2=S02  +  ^©3.     [278] 
[279] 

It  unites  with  many  metallic  oxides  to  form  sulphates,  and 
baryta  burns  in  its  vapor. 

BaO  +  ^©3  =  BaO,SO3.  [280] 

It  has  an  intense  affinity  for  water,  and  the  heat  developed  by 
the  union  is  so  gi»at  that  the  solid  hisses  like  red-hot  iron  when 
dropped  into  the  liquid.  The  product  is  common  sulphuric 
acid. 

247.  Sulphurylic  Chloride.  £02  C72.  —  May  be  formed  by 
the  direct  union  of  S02  and  Gl~Cl  under  the  influence  of  the 
sunlight,  also  by  the  reaction 

H2SO,  +  2P015  =  S02G12  +  2PCIS0  +  2HCL  [281] 

The  product  is  a  liquid  boiling  at  80°  ;  Sp.  Gr.  1.68.  Slowly 
decomposed  by  water. 


S02  C12  +  2ff20  =  ff2S04  +  2HCL  [282] 

There  have  also  been  described  the  allied  compounds 
H-0-S02Cl  and  S02I2'  The  relations  of  these  compounds 
to  sulphuric  acid  will  be  made  more  evident  by  writing  the 
symbols  thus  :  — 

HofSO*  ffo,Cl=S02,  ClfS02,  I2=S02. 

248.  Sulphuric  Acid.  ff2=02=S02  or  ffofSO*  —  The  follow- 
ing reactions  are  interesting  as  illustrating  the  constitution  of 
this  important  acid,  although  of  no  practical  value  as  methods 
of  making  it  :  — 

Ho-Ho  +  S02  —  JJOfS02,  [283] 


S03  =  H2  0,SOS.  [284] 

2ff2=  02=SO  +  0  -  0  =  2ff2=  OfSO,.  [285] 

S-S  +  ±H-0-N02  =  2H2-02=S02  +  4NO.     [286] 


§248.]  SULPHUR.  317 

For  the  uses  of  the  arts  the  acid  is  made  in  enormous  quanti- 
ties by  burning  sulphur  in  large  brick  ovens,  and  conveying  the 
S02  thus  formed,  together  with  steam  and  nitric  acid  fumes, 
generated  simultaneously  [135],  into  large  chambers  lined  with 
sheet  lead. 


1.  S02  +  2HNOZ  =  ff2S04  +  2NO?  [287] 

2.  3N02  +  ff20  =  2HN03  +  NO.  [288] 

3.  2NO  +0=0  =  2  NO?  [289] 

These  reactions  may  be  repeated  indefinitely,  and  it  is  evi- 
dent that  the  same  quantity  of  nitric  acid  would  serve  to  con- 
vert an  infinite  amount  of  S02  into  H2SO^  were  it  not  for  the 
loss  occasioned  by  the  constant  draft  of  air  through  the  cham- 
bers. The  reaction  consists  essentially  in  a  transfer  of  oxygen 
from  the  air  to  the  S0%,  the  nitrogen  compounds  acting  as  the 
mediator,  and  the  draft  yields  the  requisite  supply  of  oxygen 
gas.  When  the  amount  of  aqueous  vapor  is  insufficient,  there 
forms  in  the  chambers  a  white  crystalline  compound  of  some- 
what uncertain  composition,  but  to  which  has  been  assigned  the 
symbol  (N02)f(S02-0-S02).  When  mixed  with  water,  this 
compound  breaks  up  into  sulphuric  acid  and  nitrous  anhydride, 
so  that  the  formation  of  the  acid  may  also  be  represented  by  the 
following  equations,  which  are  thought  by  some  chemists  to  rep- 
resent the  process  more  accurately  than  those  given  above  :  — 

1.  S02  +  2ffoN02  =  ffo2S02  +  2N02.          [290] 

2.  4]V02  +  4S02  +  0-0  =  2(N02)2=(S02-0-S02).   [291] 

3.  (N02)2=(S02-  0  -S02)  +  2ff20  = 

2ffo2S02+  N203.     [292] 


4.  3N2  03+ff20=z  2ffoN02  +  4NO.  [293] 

5.  2NO  +  0-0  =  2N02.  [294] 

In  manufacturing  sulphuric  acid  iron  pyrites  is  now  frequently 
used  instead  of  sulphur.  This  ore,  burnt  in  kilns  adapted  to 
the  purpose,  yields  a  plentiful  supply  of  S02,  which  is  converted 
into  sulphuric  acid  in  lead  chambers  as  before.  The  acid  drawn 
from  the  chambers  is  very  dilute,  and  for  most  uses  must  be 


318 


SULPHUR. 


[§248. 


concentrated  by  evaporation,  which  is  begun  in  leaden  pans, 
but  completed  in  retorts  of  glass  or  platinum.  The  strongest 
acid  thus  obtained  corresponds  to  the  symbol  H2SO^.  It  is  an 
oily  liquid  (oil  of  vitriol),  Sp.  Gr.  =  1.842,  boiling  at  327°,  and 
crystallizing  at  a  low  temperature.  If  during  the  evaporation 
the  temperature  is  limited  to  205°  C.,  an  acid  is  obtained  of  the 
composition  ff2S04 .  ff20,  and  Sp.  Gr.  1.78,  which  crystallizes 
at  9°,  and  by  limiting  the  temperature  to  100°,  still  a  second 
definite  hydrate  may  be  obtained,  ff2S04 .  2ff20,  which  has  Sp. 
Gr.  =  1.62.  Oil  of  vitriol  may  be  mixed  with  water  in  any 
proportion,  and  the  hydration  of  the  acid  is  accompanied  by  a 
condensation  of  volume  and  a  great  evolution  of  heat,  the  max- 
imum of  condensation  and  the  maximum  of  heat  being  attained 
when  the  proportions  are  such  as  to  form  the  second  hydrate. 
A  definite  Sp.  Gr.  corresponds  to  each  degree  of  dilution,  and 
tables  have  been  prepared  by  which,  when  the  specific  gravity 
is  known,  the  strength  of  the  acid  may  be  determined.  The 
short  table  which  follows  gives  all  the  data  required  for  the 
problems  in  this  book :  — 


Per  Cent  of 
H2S04. 

Sp.  Gr. 
at  15^. 

Per  Cent  of 

SOy 

Per  Cent  of 
H2SOV 

Sp.  Gr. 
at  15°. 

•§ 

Per  Cent  of 

SOy 

100 

1.8426 

81.63 

50 

1.3980 

40.81 

95 

1.8376 

77.55 

45 

1.3510 

36.73 

90 

1.8220 

73.47 

40 

1.3060 

32.65 

85 

1.7860 

69.38 

35 

1.2640 

28.57 

80 

1.7340 

65.30 

30 

1.2230 

24.49 

75 

1.6750 

61.22 

25 

1.1820 

20.40 

70 

1.6150 

57.14 

20 

1.1440 

16.32 

65 

1.5570 

53.05 

15 

1.1060 

12.24 

60 

1.5010 

48.98 

10 

1.0680 

8.16 

55 

1.4480 

44.89 

5 

1.0320 

4.08 

In  consequence  chiefly  of  its  strong  attraction  for  water,  sul- 
phuric acid  disorganizes  and  blackens  both  animal  and  vegeta- 
ble tissues.  It  is  also  used  as  a  hygroscopic  agent,  and,  under 
limited  conditions,  for  the  dehydration  of  various  chemical  com- 
pounds. Its  action  on  different  chemical  agents  has  been  al- 
ready repeatedly  illustrated.  (See  [64],  [231],  [£65].)  It 
forms  several  classes  of  salts,  as  is  illustrated  by  the  following 
examples :  — 


§251.]  SELENIUM.  —  TELLURIUM.  319 

Hydro-sodic  Sulphate  ffo,Nao=S02, 

Disodic  Sulphate  Nao2=S02  and  with 

Sodic  Disulphate  Naof(SO 

Cupric  Sulphate  Cuo  =S02 . 

Ferrous  Sulphate  Feo  =S02 .  1H2  0, 
Potassio-ferrous  Disulphate         Feo=(SO=02  =SO)--Koz 

Aluminic  Sulphate  Al<pi(S02)3 .  ISH20, 

Common  Alum  £o2=(S02)^Al<p  .  24^0, 

Zincic  Sulphate  Zno=S02J 

Dizincic  Sulphate  Zno2=SO, 

Trizincic  Sulphate  Zno&iS. 

The  last  may  be  regarded  as  an  orthosulphate,  but  salts  of  this 
class  are  wholly  exceptional. 

249.  Nordhausen  Sulphuric  Acid,  ffo2=(S02-0-S02),  corre- 
sponding to  the  disulphates  in  constitution,  may  be  prepared  by 
dissolving  S03  in  IT2S04,  and  has  been  manufactured  for  many 
years  at  the  German  town  whence  it  takes  its  name,  by  the 
distillation  of  ferrous  sulphate.     The  manufacture  of  sulphuric 
acid  is  one  of  the  most  important  branches  of  industry  in  a  civ- 
ilized community,  as  there  is  hardly  an  art  or  a  trade  into  which, 
in  some  form  or  other,  it  does  not  enter. 

250.  Sulphurous  Chloride.  S2G12.  —  Yellow,  volatile,  fuming 
liquid,  formed  by  distilling  sulphur  in  an  atmosphere  of  chlorine 
gas.     It  is  a  powerful  sulphur  solvent,  and  has  been  used  for 
vulcanizing  india-rubber.     It  is  decomposed  by  water,  but  mixes 
with  benzole  and  carbonic  sulphide.     Sulphuric  chloride,  SCI& 
and  several  oxychlorides  of  sulphur  are  also  known. 

251.  SELENIUM.    Se  —  79.4.     TELLURIUM.     Te  = 
128.  —  Two  very  rare  elements,  closely  allied  to  sulphur,  but 
presenting  such  differences  as  might  be  anticipated  in  elements 
of  the  same  chemical  series.     They  form  compounds  with  hy- 
drogen, H2Se  and  ff2  Te,  analogous  to  ff2S,  and  compounds  with 
oxygen  and  hydrogen  resembling  sulphurous  and  sulphuric  acids. 

Selenium,  which  follows  in  the  series  next  to  sulphur,  mani- 
fests its  relationship  in  many  ways.  The  elementary  substance, 
which  in  its  ordinary  condition  is  a  brittle  solid  having  a  glassy 
fracture  and  a  dark  brown  color,  Sp.  Gr.  4.3,  may  be  obtained 
in  several  allotropic  states,  and  in  one  of  these,  when  its  Sp.  Gr. 


320  SELENIUM.  —  TELLURIUM.  [§251. 

=  4.8,  it  has  the  same  monoclinic  form  and  molecular  volume l 
as  the  corresponding  condition  of  sulphur.  It  readily  melts  at 
a  varying  temperature  above  100°,  depending  on  its  condition, 
and  at  700°  is  converted  into  a  deep  yellow  vapor  which  has 
been  observed  to  have,  at  a  high  temperature,  Sp.  Gr.  =  82.  It 
burns  in  the  air  with  a  blue  flame,  forming  chiefly  Se  0^  and 
emits  an  offensive  odor  resembling  putrid  horseradish.  Hydric 
selenide,  also,  is  a  gas  with  a  disgusting  smell,  which,  like  ff2S, 
precipitates  many  of  the  metals  from  solutions  of  their  salts  as 
selenides.  Selenic  acid  is  a  thick  oily  liquid  like  sulphuric  acid, 
and  many  of  the  selenates  cannot  be  distinguished  by  merely 
external  characters  from  the  corresponding  sulphates.  Sele- 
nium, moreover,  is  almost  invariably  found  in  nature  associated 
with  sulphur,  and  is  extracted  from  the  residues  resulting  from 
the  treatment  of  sulphur  ores.  There  are,  however,  a  few  rare 
minerals  which  consist  mainly  of  metallic  selenides.  Among 
the  most  important  of  these  may  be  named  Clausthalite,  PbSe, 
Berzelianite,  CuSe,  Naumannite,  Ag%Se,  and  Onofrite,  HgSe. 

When  we  descend  in  the  series  to  Tellurium,  we  find  more 
marked  differences.  The  elementary  substance  has  a  silver- 
white  color,  a  bright  metallic  lustre,  and  outwardly  resembles  a 
metal.  It  is  closely  allied  in  many  of  its  physical  properties  to 
bismuth.  It  crystallizes  in  rhombohedrons,  and  the  mineral 
Tetradymite  has  been  regarded  as  an  isomorphous  mixture  of 
native  tellurium  with  native  bismuth.  Its  Sp.  Gr.  =  6.2,  and 
its  atomic  volume  is  very  much  nearer  that  of  bismuth  and  an- 
timony, than  that  of  selenium  and  sulphur.  Nevertheless,  in 
other  relations  it  is  closely  allied  to  selenium.  It  is  hard  and 
brittle,  a  poor  conductor  of  heat  and  electricity.  It  fuses  be- 
tween 425°  and  475°,  and  at  a  high  temperature  yields  a  yellow 
vapor  which  has  a  specific  gravity  corresponding  to  the  molec- 
ular formula  Te=Te.  When  heated  in  the  air,  it  burns  with  a 
greenish  blue  flame,  and  is  converted  into  tellurous  anhydride, 
Te  02.  Lastly,  hydric  telluride  resembles  closely  hydric  sele- 
nide, and  the  salts  of  tellurous  and  telluric  acids  are  similar  to  the 
corresponding  selenites  and  selenates  ;  but  telluric  acid  does  not, 
like  selenic  acid,  form  salts  corresponding  to  the  alums,  and  its 

l  The  quotients  obtained  by  dividing  the  molecular  weights  of  different 
solid  substances  by  their  respective  specific  gravities  may  be  regarded  as 
proportional  to  their  molecular  volumes  in  the  solid  state. 


§252.]  MOLYBDENUM.  321 

salts  are  less  stable.  Tellurium  is  the  chief  constituent  of  a  few 
native  compounds  which  are  highly  prized  as  minerals.  Be- 
sides Tetradymite,  Bi^Te^  we  have  Hessite,  AgzTe,  Sylvanite, 
AgAuTe^  Altaite,  PbTe,  and  Nagyagite,  which  is  a  sulphotel- 
luride  of  lead  and  gold  of  somewhat  uncertain  composition. 
The  elements  of  this  group  form  then,  evidently,  a  very  well- 
marked  series,  in  which,  as  in  the  chlorine  series,  the  chemical 
energy  diminishes  as  the  atomic  weight  increases. 


Division  III. 

252.  MOLYBDENUM.  Mo  =  $G.  One  of  the  rarer  ele- 
ments, but  not  unfrequently  met  with  in  the  mineral  kingdom, 
usually  in  combination  with  sulphur  forming  the  mineral  Molyb- 
denite, MbS2,  which  so  closely  resembles  foliated  graphite  that 
the  two  might  easily  be  mistaken  for  each  other.  From  this 
mineral  we  readily  obtain  by  roasting,  at  a  low  red  heat  in  a 
current  of  air,  molybdic  anhydride,  Mo03,  which  is  the  most 
characteristic  compound  of  the  element.  When  pure,  the  an- 
hydride is  a  pale  buff-colored  powder,  fusing  to  a  straw-colored 
glass  at  a  red  heat,  and  volatilizing  at  a  higher  temperature.  It 
is  only  sparingly  soluble  in  water,  but  readily  dissolves  in  ordi- 
nary acids,  in  aqua  ammonia,  and  in  solutions  of  the  alkaline 
hydrates  or  carbonates,  and  forms  with  metallic  oxides  a  nu- 
merous class  of  salts  called  molybdates.  Plumbic  molybdate 
(Wulfenite),  Pb=0.2=MoO^  is  sometimes  found  in  beautiful  yel- 
low or  red  crystals  associated  with  other  lead  ores,  and  molyb- 
date of  ammonia,  (Nff4)2=02=Mo02,  is  much  used  in  the  labor- 
atory as  a  test  for  phosphoric  acid.  Besides  Mo03,  the 
element  also  forms  compounds  with  one  and  with  two  atoms 
of  oxygen,  MoO  and  MoO^  which  act  as  basic  anhydrides, 
and  there  is  also  an  intermediate  oxide  having  a  beautiful 
blue  color,  and  another  having  a  dull  green  color,  which  are 
formed  by  the  action  of  SnCl2  and  other  reducing  agents  on 
acid  solutions  of  the  molybdates,  and  the  accompanying  change 
of  color  serves  as  a  very  striking  test  for  molybdenum.  In  so- 
lutions of  molybdic  acid  or  of  molybdates,  when  acidified  with 
hydrochloric  acid,  ff2S,  gives  a  brownish-black  precipitate  of 
Mo 83,  and  there  is  still  a  third  sulphide,  MoS^  which,  as  well 
14*  u 


322  TUNGSTEN.  [§  253. 

as  the  last,  acts  as  a  sulphur  acid.  There  are  also  two  chlorides, 
Mo  (74  and  Mo  C?4.  The  elementary  substance  is  a  brittle  silver- 
white  metal  (Sp.  Gr.  =  8.6),  which  is  unalterable  in  the  air  and 
very  infusible.  It  can  be  obtained  without  difficulty  by  redu- 
cing the  oxides  with  charcoal  or  hydrogen,  but  unless  the  tem- 
perature is  very  high  the  metal  is  left  as  a  gray  powder.  The 
name  is  from  the  Greek,  and  signifies  ';  a  mass  of  lead." 

253.  TUNGSTEN.  W=  184.  — This  element  occurs  in 
tolerably  large  quantities  combined  with  calcium  in  the  mineral 
Scheelite,  Ca  JF04,  and  with  both  iron  and  manganese  in  Wol- 
fram, of  which  there  are  two  varieties,  2Fe  WO+-\-  3Mn  W04 
and  ±Fe  W04  -f-  Mn  W04.  Both  minerals  are  decomposed  by 
acids,  and  by  this  means  we  readily  obtain  tungstic  anhydride, 

JF03,  a  yellow  powder  insoluble  in  water  and  acids,  but  readily 
dissolving  in  ammonia  and  solutions  of  alkaline  hydrates,  and 
even  decomposing  with  effervescence  the  alkaline  carbonates, 
when  heated  in  solutions  of  their  salts.  From  a  boiling  alkaline 
solution  of  tungstic  anhydride  the  common  acids  throw  down  a 
yellow  precipitate  of  tungstic  acid,  H2  W04.  This  acid  forms 
with  bases  a  numerous  class  of  salts  called  tungstates,  which, 
although  of  little  practical  importance,  are  theoretically  very 
interesting,  and  have  been  the  object  of  careful  investigation. 
There  are  several  (at  least  two)  distinct  types  of  these  salts, 
and  there  are  also  two  modifications  of  tungstic  acid ;  for,  be- 
sides the  ordinary  insoluble  condition,  both  molybdic  and  tung- 
stic acids  have  been  obtained  in  a  colloidal  condition,  in  which 
they  are  very  soluble  in  water  (57).  The  tungstates  have  the 
same  crystalline  form  as  the  corresponding  molybdates,  and  a 
tungstate  of  lead,  isomorphous  with  Wulfenite,  is  a  well-known 
mineral  called  Scheeltine.  Besides  W03  there  is  an  oxide,  W02, 
which  also  acts  as  an  acid  anhydride,  and  there  is  also  an  inter- 
mediate oxide  of  a  splendid  blue  color,  which  may  be  produced 
by  the  action  of  reducing  agents  on  the  anhydride  or  the  soluble 
tungstates.  Tungsten  is  not,  like  molybdenum,  precipitated  by 
ff2S,  but  the  sulphide,  WS2,  has  been  prepared  artificially,  and 
resembles  very  closely  the  native  molybdenite.  There  is  also 
a  sulphide,  WS&  and  there  are  two  volatile  chlorides,  WCl±  and 

WC18.  The  metal  itself  (Sp.  Gr.  17.6)  is  easily  reduced,  but, 
in  consequence  of  its  great  infusibility,  cannot  be  obtained  in  a 
compact  state  except  at  a  very  high  temperature.  It  has  an 


§253.]  QUESTIONS  AND  PROBLEMS.  323 

iron-gray  color,  and,  when  alloyed  with  steel  to  the  extent  of  8 
or  10  per  cent,  renders  the  metal  exceedingly  hard.  The  com- 
pounds neither  of  tungsten  nor  of  molybdenum  have  found  any 
important  applications  in  the  arts,  although  sodic  tungstate  has 
been  used,  mixed  with  starch,  in  finishing  cambrics,  because  it 
has  been  found  to  render  these  light  fabrics  less  inflammable. 
The  name  tungsten  had  a  Swedish  origin,  and  signified  in  the 
original  "  heavy  stone." 


Questions  and  Problems. 

1.  What  is  the  per  cent  of  sulphur  in  gypsum  and  iron  pyrites? 

Ans.  18.6  per  cent  and  53.33  per  cent. 

2.  Write  the  symbols  of  the  different  classes  of  sulphides. 

3.  Express  by  graphic  symbols  the  constitution  of  the  various  sul- 
phur radicals. 

4.  What  are  the  atomic  volumes  of  the  two  crystalline  varieties  of 
sulphur?  Ans.  15.60  and  16.16. 

5.  By  heating  10.000  grammes  of  silver  in  the  vapor  of  sulphur, 
Dumas  obtained  11.4815  grammes  of  argentic  sulphide.     What  is  the 
atomic  weight  of  sulphur  ?     What  assumption  is  made  in  your  calcu- 
lation, and  what  ground  have  you  for  this  assumption  ? 

Ans.  32.000. 

6.  What  is  the  specific  gravity  of  H^S  gas  referred  to  hydrogen 
and  to  air?  Ans.  17  and  1.1764. 

7.  What  weight  of  sulphur  is  contained  in  one  litre  of  H2S  ? 

Ans.  1.434  grammes. 

8.  How  much  antimonious  sulphide  is  required  for  the  preparation 
of  one  litre  of  hydric  sulphide  ?  How  much  to  prepare  340  grammes  ? 

Ans.  5.076  grammes,  1133.33  grammes. 

9.  What  volume  of  oxygen  gas  is  required  to  burn  one  litre  of 
H2S,  and  what  are  the  volumes  of  the  aeriform  products  ? 

Ans.  1|  litres  of  oxygen  gas,  one  litre  of  aqueous  vapor,  and  one 
of  sulphurous  anhydride. 

10.  One  litre  of  (H^S  -4-  Aq)  saturated  at  0°  will  absorb  what 
volume  of  oxygen  gas,  and  will  yield  what  weight  of  sulphur?. 

Ans.  2.185  litres,  6.263  grammes. 

11.  Assuming  that  a  solution  of  iodine  in  a  solution  of  potassic 
iodide  has  been  prepared  of  known  strength,  how  may  this  be  used 
to  measure  the  quantity  of  H^S  in  a  mineral  water  ? 


324  QUESTIONS  AND  PROBLEMS. 

12.  The  specific  gravity  of  hydric  sulphide  has  been  found  by  ex- 
periment to  be  17.2,  and  by  reaction  [243]  it  is  shown  that  one  vol- 
ume of  the  gas  contains  an  equal  volume  of  hydrogen.     Show  that 
these  results  agree  quite  closely  with  the  molecular  symbol  assigned 
to  the  compound.     How  do  you  explain  the  slight  discrepancy  ? 

1 3.  Write  the  reactions  by  which  hydric  sulphide  is  formed  from 
calcic  sulphate. 

14.  Write  the  reaction  by  which  NH^-Hs  may  be  formed  from 
aqua  ammonia. 

15.  Write  the  reaction  of  HZS  gas  on  solution  of  plumbic  acetate, 
and  calculate  what  volume  of  (H2  <S  -j-  A  q)  saturated  at  0°  would  be 
required  to  precipitate  0.207  grammes  of  lead. 

Ans.  5.109  cTm:8  of  H2S  -j-  Aq. 

16.  Write  the  reaction  of  H^S  on  solution  of  acetate  of  zinc. 
What  inference  would  you  draw  from  the  fact  that  Zn  is  precipitated 
by  this  reagent  from  an  acetic  acid  solution,  while  Fe  and  Mn  are 
not? 

17.  Into  what  groups  may  the  metallic  radicals  be  divided  by 
means  of  the  two  reagents  hydric  sulphide  and  ammonic  sulphide, 
and  how  must  the  reagents  be  used  in  order  to  separate  these  groups 
from  a  given  solution  ? 

18.  In  reducing  28  grammes  of  iron  from  the  condition  of  ferric 
to  that  of  ferrous  chloride,  how  much  sulphur  is  precipitated? 

Ans.  8  grammes. 

19.  Analyze  the  reactions  [248]  and  [249],  and  show  how  the 
HZS  gas  acts  as  a  reducing  agent  in  each  case. 

20.  Write  the  reaction  of  hydrochloric  acid  on  sodic  bisulphide. 

21.  Eepresent  by  graphic  symbols  the  constitution  of  the  various 
potassic  sulphides. 

22.  Analyze  reactions  [250]  to  [263]. 

23.  Write  reaction  when  sulphur  and  milk  of  lime  are  boiled  to- 
gether, assuming,  first,  that  CaS2,  and  second,  that  CaS5,  is  produced. 

24.  Write  reaction  when  sulphur  and  calcic  hydrate  are  melted 
together,  assuming  that  CaS&  and  CaSO±  are  produced. 

25.  Represent  by  graphic  symbols  the  composition  of  the  com- 
pounds of  sulphur  and  oxygen. 

26.  Is  the  quantivalence  of  sulphur  in  the  sulphites  and  hyposul- 
phites the  same  as  in  the  sulphates,  &c.  ? 


QUESTIONS  AND  PKOBLEMS.  325 

27.  What  volume  of  sulphurous  anhydride  would  be  formed  by- 
burning  2.8672  grammes  of  sulphur?  Ans.  2  litres. 

28.  It  has  been  observed  that  when  sulphur  burns  in  oxygen  the 
volume  of  the  product  is  the  same  as  the  initial  volume  of  oxygen 
gas.     It  has  been  found  by  experiment  that  the  Sp.  Gr.  of  sulphur- 
ous anhydride  equals  32.25.     How  do  these  facts  correspond  with  the 
molecular  symbol  usually  assigned  to  the  compound  ?     What  is  the 
0JJ.  (£>r.  of  S0t  referred  to  air?  Ans.  2.234. 

29.  How  much  mercury  is  required  to  make  one  litre  of  502  ? 

Ans.  8.96  grammes. 

30.  Leaving  out  of  view  the  value  of  the  mercury  used,  as  it  may 
be  easily  recovered,  by  which  of  the  two  reactions  [265]  or  [266] 
may  SOZ  be  most  profitably  prepared  ? 

31.  How  much  Mn02  would  be  required  to  yield  by  reaction  [267] 
sufficient  $02  to  neutralize  1.29  grammes  of  sodic  carbonate? 

Ans.  1.059  grammes. 

32.  Point  out  the  volumetric  relations  in  reaction  [268]. 

33.  Are  the  conditions  under  which  the  reaction  [269]  is  obtained 
in  any  way  peculiar  ? 

34.  Compare  reactions  [271]  and  [272],  and  inquire  whether  a 
method  of  volumetric  analysis  based  upon  them  might  not  be  devised. 

35.  Represent  by  graphic  symbols  the  sulphites  whose  symbols  are 
given  in  (244). 

36.  The  refuse  lime  of  the  gas  and  alkali  works  contains  calcic 
disulphide,  CaSz.     In  what  way  would  this  be  changed  by  exposure 
to  the  air  into  calcic  hyposulphite,  and  how  from  this  product  could 
sodic  hyposulphite  be  prepared  ? 

37.  Write  the  reaction  of  hydrochloric  acid  on  sodic  hyposulphite, 
knowing  that  hyposulphurous  acid,  when  liberated,  breaks  up  into 
sulphurous  anhydride  and  sulphur. 

38.  The  specific  gravity  of  the  vapor  of  sulphuric  anhydride  has 
been  found  by  experiment  to  be  39.9.     How  does  this  agree  with  the 
theoretical  value  ?     Compare  the  densities  of  0=0,  SO^  and  S03  as 
regards  the  relative  degree  of  condensation  in  each. 

39.  What  are  the  relations  of  the  compounds  S02C72,  SOZCIHO, 
S08,  and  HZSO^  to  each  other? 

40.  Analyze  the  two  sets  of  reactions  [287  et  seq."]  and  [290  et  seqJ], 
and  show  from  whence  the  oxygen  required  to  oxidize  the  sulphur- 
ous acid  is  derived,  and  what  part  the  oxides  of  nitrogen  play  in  the 
process. 


326  QUESTIONS  AND  PROBLEMS. 

41.  In  the  process  of  making  oxygen  gas  from  sulphuric  acid,  from 
whence  is  the  oxygen  in  the  first  instance  derived  ?     Might  not 
the  same  quantity  of  acid  be  made  to  yield  an  indefinite  supply 
of  gas  ? 

42.  It  appears  by  experiment  that  the  Sp.  Gr.  of  HZSO^  vapor  is 
24.42.     How  does  this  agree  with  theory,  and  how  do  you  explain 
the  discrepancy  ? 

43.  It  has  been  found  by  exact  experiments  that  100  parts  of  lead 
yield  146.45  parts  of  plumbic  sulphate.      What  is  the  molecular 
weight  of  sulphuric  acid  ?     What  assumption  does  your  calculation 
involve  (68)  ?     Why  do  you  regard  this  result  as  more  trustworthy 
than  that  of  the  last  problem  ?  Ans.  98.16. 

44.  How  do  the  symbols  of  the  hydrates  of  sulphuric  acid  compare 
with  those  of  the  crystalline  salts  of  this  acid  ? 

45.  Write  the  symbols  of  sulphuric  acid  and  its  two  hydrates,  rep- 
resenting them  as  compounds  of  SO^  with  hydroxyl.     Point  out  the 
distinction  between  the  ortho  and  meta  acids,  and  show  that  a  simi- 
lar distinction  may  be  made  among  the  salts. 

4.6.  How  many  litres  of  sulphuric  acid,  Sp.  Gr.  =  1.615,  can  be 
made  from  1,000  kilos,  of  pyrites,  assuming  that  all  the  sulphur  in  the 
mineral  is  burnt  ?  Ans.  1444.4  litres. 

47.  How  much  sulphuric  acid  by  weight,  Sp.  Gr.  =  1.501,  will  be 
required,  1st.  To  neutralize  53  grammes  of  sodic  carbonate?  2d.  To 
dissolve  32.6  grammes  of  zinc '?  3d.  To  precipitate  completely  2.08 
grammes  of  baric  chloride  ? 

Ans.  81.666  grammes,  81.666  grammes,  1.633  grammes. 

48.  Represent  the  constitution  of  the  various  sulphates  by  graphic 
symbols. 

49.  In  what  does  the  symbol  of  dizincic  sulphate  differ  from  that 
of  a  sulphite  ? 

50.  If  the  specific  gravity  and  molecular  weight  of  a  solid  sub- 
stance be  given,  how  can  you  find  the  molecular  volume  of  the 
substance  in  the  solid  condition  ? 

51.  How  does  the  molecular  volume  of  sulphur  compare  with  that 
of  selenium,  1st.  In  the  solid  condition  ?  2d.  In  the  crystalline  con- 
dition ? 

52.  What  is  true  of  the  molecular  volumes  of  all  substances  in  the 
state  of  gas  ? 

53.  Compare  the  molecular  volumes  of  tellurium  and  bismuth. 


QUESTIONS  AND  PROBLEMS.  327 

54.  What  are  the  analogies,  and  what  are  the  chief  points  of  dif- 
ference between  sulphur,  selenium,  and  tellurium  ? 

55.  Write  the  reaction  of  hydric  selenide  on  a  solution  of  plumbic 
acetate,  also  of  potassic  selenate  on  a  solution  of  baric  chloride  ? 

56.  Write  the  reaction  when  Molybdenite  is  roasted  in  the  air. 

57.  Write  the  reaction  of  HZS  on  a  solution  of  molybdic  acid  in 
hydrochloric  acid. 

58.  What  is  the  relative  proportion  of  tungstic  anhydride  in  the 
two  varieties  of  Wolfram  ?  Ans.  76.47  to  76.38  %. 

59.  Write  the  reaction  of  hydrochloric  acid  on  Scheelite. 

60.  In  what  respects  does  tungsten  resemble  molybdenum  ? 

61.  What  is  the  atomicity  of  tungsten  and  molybdenum,  and  what 
is  the  prevailing  quantivalence  in  each  case  ? 


328  COPPER.  [§254. 


Division  IV. 

254.  COPPER.  Ou  =  63.5.  —  Dyad.  One  of  the  most 
abundant  metals,  and  known  from  great  antiquity.  Of  its  ores, 
by  far  the  most  important  is  Copper  Pyrites,  Fe=Sz-Cu,  which 
is  found  to  a  greater  or  less  extent  in  almost  all  countries. 
This  mineral  resembles  iron  pyrites,  but  is  distinguished  from 
it  by  greater  softness  and  a  ruddier  tint.  The  smelting  of  the 
ore  is  a  complex  process,  and  consists  in  an  alternating  series 
of  roastings  and  meltings,  during  which  the  iron  passes  into  the 
slags,  while  the  copper  accumulates  in  the  successive  "mattes," 
as  they  are  called,  until  at  last  a  nearly  pure  sub-sulphide  is 
obtained.  This  is  now  heated  in  a  current  of  air  until  the  metal 
is  partially  oxidized,  and  then  the  mass  is  melted,  when  the 
following  reaction  results  :  — 


2  Ou  0  +  Cu^S  =  4Cu  +  S02.  [295] 

The  crude  metal  thus  obtained  must,  however,  be  subsequently 
refined.  To  this  end  it  is  first  kept  melted  in  the  air  for  many 
hours,  until  all  the  impurities  are  oxidized  ;  and  then  the  oxides 
of  copper,  formed  at  the  same  time,  are  reduced  by  submitting 
the  mass  to  the  action  of  carbonaceous  gases,  which  are  gener- 
ated by  thrusting  a  stick  of  green  wood  under  the  molten  metal. 
255.  Metallic  Copper.  Cu.  —  Found  native  crystallized  in 
forms  of  the  isometric  system.  Has  a  brilliant  lustre,  and  a 
familiar  reddish  color.  Has  great  hardness  and  tenacity.  Is 
very  ductile  and  malleable,  and  one  of  the  best  conductors  of 
heat  and  electricity.  Sp.  Gr.  8.8.  Fuses  at  about  780°.  Vol- 
atilizes only  at  a  very  high  temperature.  Its  vapor  burns  with 
a  beautiful  green  flame,  which  shows  in  the  spectroscope  char- 
acteristic bands.  Under  ordinary  conditions  copper  undergoes 
no  change  in  the  atmosphere,  but  if  heated  to  redness  in  the  air 
it  is  rapidly  oxidized.  In  presence  of  acids  or  solutions  of  chlo- 
rides, like  sea-water,  copper  absorbs  oxygen  from  the  air  at  the 
ordinary  temperature,  and  is  more  or  less  rapidly  corroded.  A 
similar  effect  is  also  produced  by  aqua  ammonia  and  solutions 
of  ammonia  salts.  Out  of  contact  with  the  air,  dilute  hydro- 
chloric or  sulphuric  acids  have  but  little  action  upon  metallic 


§  257.]  COPPER.  329 

copper.  If  boiled  with  strong  hydrochloric  acid,  it  very  slowly 
dissolves  with  the  evolution  of  hydrogen  gas.  Under  the  same 
conditions  sulphuric  acid,  if  not  too  dilute,  is  decomposed  by  it, 
cupric  sulphate  is  formed,  sulphurous  acid  is  evolved,  and  the 
reaction  is  similar  to  [265].  "Nitric  acid  is  the  best  solvent, 
but,  singularly,  the  strongest  acid  has  no  action  on  the  metal. 
When  diluted  with  water,  however,  the  action  is  very  violent; 
cupric  nitrate  is  formed,  and  a  gas  is  evolved  which  is  generally 
NO  ;  but  when  the  acid  is  very  dilute  this  product  is  more  or 
less  mixed  with  N20. 

256.  Cupric  Oxides.  \_Cuz~\0  and  OuO.  —  Both  of  which  act 
as  basic  anhydrides,  although  the  salts  of  the  second  are  by  far 
the  most  stable  and  important  compounds.  [  Cu^\  0  has  a  red 
color,  and  when  melted  into  glass  imparts  to  it  a  beautiful  ruby 
or  purple  color.  It  is  the  Red  Oxide  of  Copper  of  mineralogy, 
and  is  found  massive  and  beautifully  crystallized  in  various 
forms  of  the  isometric  system,  also  in  splendid  capillary  tufts 
(Chalcotrichite).  CuO  is  black,  but  imparts  to  glass  a  green 
color.  It  is  found  sparingly  in  nature,  rarely  crystallized 
{Black  Oxide  of  Copper,  or  Melaconite).  May  be  prepared  by 
roasting  copper  or  igniting  the  nitrate.  Is  very  easily  reduced 
by  hydrogen  £67]  or  carbonaceous  materials,  and  is  much  used 
as  an  oxidizing  agent  in  the  process  of  organic  analysis.  The 
following  reactions  illustrate  some  of  the  relations  of  these 
oxides  and  their  hydrates:  — 

When  cold,  (Cu=02=SOs  +  lK-O-H-\-  Aq)  = 

CuO2H2  +  (KfOfSOt+Ag).  [296] 

Byboiling,  (Ou  =  0?ffa+Ag)  =  CuO+(ffaO+Ag).   [297] 


By  boiling  with  grape  sugar, 

2=S0.2+  1K-0-H—  0+Aq)  = 

[Cu2]O  +  (2KfOfSOs  +  2ff20  +  Aq).  [298] 


Bed. 


An  orange-yellow  hydrate,  4[(7w2]O.  /ZjO,  is  precipitated  on 
first  warming  the  liquid,  but  this  is  rendered  anhydrous  'by 
boiling. 

257<    Cupric  Sulphate  (Blue  Vitriol).  Cu=OfS02  .  5ff20.— 
The  most  important  soluble  salt  of  copper.   Although  when  pure 


330  COPPER.  [§  258. 

it  always  crystallizes  with  five  molecules  of  water,  as  above,  yet 
it  is  capable  of  forming  isomorphous  mixtures  with  ferrous  sul- 
phate, Fe  =  02=S02  .  1H20.  When  in  this  mixture  the  copper  ia 
in  excess,  the  crystals  take  5ff20  and  the  form  of  cupric  sul- 
phate (Fig.  28).  If,  however,  the  iron  is  in  excess,  they  take 
1H20  and  the  form  of  ferrous  sulphate,  similar  to  Fig.  26.  The 
anhydrous  salt  is  white,  but  becomes  blue  on  uniting  with  water, 
for  which  it  has  a  very  strong  affinity.  Of  the  five  molecules 
of  water  with  which  the  crystalline  salt  is  united,  one  is  held 
much  more  firmly  than  the  other  four,  and  may  be  replaced  by 
a  molecule  of  an  alkaline  sulphate.  This  gives  a  reason  for 
writing  the  symbol  of  the  salt  thus,  Ho2,Cuo^SO  .  4H20.  In 
like  manner  the  symbols  of  several  so-called  basic  salts  may  be 
written  thus, 

Ho,(Cu02ff)3iSO, 
Hoz,(CuOzH}^S  (Brochantite), 
Ho,(Cu02ff)5lS.2ff20, 

in  which  the  group  Cu02H  acts  as  a  monad  radical.  From 
solutions  of  cupric  sulphate  the  copper  is  readily  precipitated 
by  Zn  or  Fe. 

Zn  +  (CuSO,  +  Aq)  =  Cll  +  (ZnS04  +  Aq).  [299] 

258.  Carbonates.  —  Malachite,  (  Ou  02ff)2=  CO.     Same  com- 
pound may  be  obtained  by  mixing  hot  solutions  of  cupric  sul- 
phate   and    sodic    carbonate.       Azurite,     Cuo&Ho2™C2    or 
Ho,Cuo  =  C-Cuo-C=Cuo,Ho.     Mysorin,   Cuo2=C.     The  normal 
carbonate  is  not  known. 

259.  Nitrates.  —  Cuo=(N02)2  .  QJT20  when  crystallized  be- 
low 60°,  and  Cuo=(N02)2.3ff20  when  crystallized  above  60°, 
a  deliquescent  blue  salt.     A  green  basic  nitrate  has  the  symbol 


260.  Cupric  Phosphate,  Cuosl(PO)2,  is  obtained  on  adding 
a  solution  of  sodic  phosphate  to  a  solution  of  cupric  sulphate. 

261.  Cupric  Silicate.    Dioptase,  Ho,(Cu02H)=SiO. 

262.  Sulphides:-— 

Copper  Glance  [Cu^S, 

Covelline  (Indigo  Copper)  CuS, 

Copper  Pyrites  Fe=S2=Cu, 

Erubescite  Fe  =$=([  CkJ  -S-[  CfcJ), 

Tetrahedrite  [  OuJ^S6  1  Sb2  .  ZnS. 


§2G7.]  COPPER.  331 

When  H2S  is  passed  through  the  solution  of  a  copper  salt,  a 
black  precipitate  falls  having  the  composition  Cu^S^IIo^  which 
rapidly  oxidizes  in  the  air. 

263.   Fluohydrate  of  Copper.    (CuOH)-Fl. 

Chlorides.  —  Cuprous  Chloride,  [<7w2]  01%.  White  compound, 
insoluble  in  water,  crystallizes  in  tetrahedrons.  Cupric  Chloride, 
CuCl2  .  2ff20,  crystallizes  in  green  needles,  very  soluble  in  both 
water  and  alcohol.  Cupric  Oxichloride,  (  Cu4  03)=  C12  .  ^Hz  0,  is 
much  used  as  a  paint  (Brunswick  green),  and  the  mineral  Atac- 
amite  is  the  same  compound,  with  only  one,  or  at  most  two,  mole- 
cules of  J?20. 

264.  Cupric  Hydride.  CuJT2.  —  A  brown  powder,  which  gives, 
with  hydrochloric  acid,  the  following  remarkable  reaction  :  — 

CuJHa+(2ffOl  +  Ag)  =  (OuOla+Aq)  -\-2ff-ff.    [300] 

265.  Ammoniated  Compounds.  —  When  a  solution  of  ammo- 
nia or  of  ammonia  carbonate  is  added  to  a  solution  of  a  salt  of 
copper,  the  light-green  precipitate  first  produced  readily  dis- 
solves in  an  excess  of  the  reagent,  producing  a  deep-blue  solu- 
tion ;  and  this  striking  coloration  is  one  of  the  most  characteristic 
tests  of  the  presence  of  copper.     The  effects  are  caused  by  the 
formation  of  certain  remarkable  compounds,  in  which  a  portion 
of  the  hydrogen  of  the  ammonia  appears  to  have  been  replaced 
by  copper.     The  following  are  a  few  examples:  — 


,  .  ff,0. 

266.  Characteristic  Reactions.  —  The  presence  of  copper  in 
a  solution  may  be  readily  detected,  not  only  by  ammonia  as  in- 
dicated above,  but  also  by  the  action  of  polished  iron  (a  needle, 
for  example),  which,  in  a  feebly  acid  solution,  soon  becomes 
covered  with  a  red  metallic  coating.     Copper  ores,  when  mixed 
with  fluxes,  are  readily  reduced  on  charcoal  before  the  blow- 
pipe, and  this  is  one  of  the  best  means  of  recognizing  such 
compounds. 

267.  Uses.  —  Besides  the  numerous  uses  of  the  metal  itself, 
copper  is  employed  in   the  arts  still  more  extensively  when 
alloyed  with  other  metals.     The  varieties  of  brass  and  yellow 
metal  are  alloys  of  copper  and  zinc  in  different  proportions, 


332  MERCUEY.  [§  268. 

while  bronze,  bell-metal,  gun-metal,  and  speculum-metal  are  all 
essentially  alloys  of  copper  and  tin.  Several  of  the  compounds 
of  copper  are  much  used  as  paints. 

268.  MERCURY.     Ify  =  200.  —  Dyad.     This  element  is 
not  widely  disseminated,  but  its  ores  are  abundant  in  a  few  lo- 
calities, of  which  the  most  noted  are  Idria  in  Austria,  Almaden 
in  Spain,  New  Almaden  in  California,  and  Huancavelica  in  Peru. 
The  ores  at  all  these  localities  consist  chiefly  of  Cinnabar,  HgS, 
but  they  frequently  contain  a  small  quantity  of  the  metal  in  the 
native  state.     They  are  easily  smelted,  the  sulphur  of  the  ore 
serving  as  fuel.     The  assorted  ores  are  arranged  in  layers  in 
kilns  of  peculiar  construction,  and  the  mass  kindled  with  brush- 
wood.    As  the  sulphur  burns  away,  the  mercury  is  volatilized, 
and  the  products  thus  formed  are  passed  through  earthen  pipes 
("aludels")  or  brick  chambers,  which  condense  the  mercury 
vapor,  while  the  S02  gas  escapes  into  the  atmosphere. 

ffgS+  0*0  =  ffff+SO*  [301] 

In  the  Palatinate,  mercury  is  obtained  from  cinnabar  by  mixing 
the  ore  with  slaked  lime  and  distilling  in  iron  retorts. 

4ffgS  +  4 CaO  =  3  CaS  +  CaS04  -f  Hg.      [302] 

269.  Metallic  Mercury.  Hg.  —  The  only  metal  liquid  at  or- 
dinary temperatures.     Freezes  at  — 40°.     Boils  at  350°  and 
evaporates,  but  only  with  exceeding  slowness  at  the  ordinary 
temperature.     Sp.  Gr.  of  liquid,  13.596.     Sp.  Gr.  of  vapor  by 
experiment,  100.7.    Has  a  brilliant  metallic  lustre,  silver-white 
color.  In  solid  condition  is  malleable,  crystallizes  in  octahedrons, 
Sp.  Gr.  14.4.     In  contact  with  the  air  pure  mercury  undergoes 
no  change  at  the  ordinary  temperature,  but  if  boiled  in  the  at- 
mosphere, it  is  slowly  converted  into  HgO.     Hydrochloric  acid 
is  without  action  on  the  metal,  and  the  same  is  true  of  dilute 
sulphuric  acid.     Strong  sulphuric  acid,  however,  is  decomposed 
by  it  [265].     The  best  solvent  is  nitric  acid,  which  yields  dif- 
ferent products  according  to  the  proportions  of  metal,  acid,  and 
water  used.     Chlorine,  Bromine,  Iodine,  and  Sulphur  all  enter 
into  direct  union  with  mercury.     By  simple  trituration  the  liquid 
metal  admits  of  being  mechanically  mixed  in  a  state  of  minute 
subdivision  with  chalk  and  with  saccharine  or  oleaginous  sub- 


§  272.]  MERCURY.  333 

stances,  and  many  important  pharmaceutical  preparations  are 
made  in  this  way,  —  blue-pills,  mercurial  ointments,  etc. 

270.  Oxides  of  Mercury.  —  Mercurous   Oxide,    [_Hg2~\0. 
Black  powder,  very  unstable.    Decomposed  by  exposure  to  light 
or  to  a  very  gentle  heat.      \_Hg2~\  0  =  Hg  0  -f-  Hg.     Mercuric 
oxide,  Hg  0.  Red  crystalline  scales  or  yellow  powder,  according 
to  mode  of  preparation.     Stable  compound,  but  decomposed  at 
red  heat  into  mercury  and  oxygen  [228].     No  corresponding 
hydrates  are  known,  but  both  oxides  form  stable  salts. 

271.  Nitrates.  —  Mercurous  nitrate  is  obtained  by  dissolving 
metallic  mercury  in  an  excess  of  nitric  acid  diluted  with  four  or 
five  times  its  bulk  of  water.     Mercuric  nitrate  is  best  obtained 
by  dissolving  mercuric  oxide  in  an  excess  of  nitric  acid.     These, 
like  other  salts  of  mercury,  tend  to  form  basic  compounds. 

Mercurous  Nitrate 
Dimercurous  Nitrate 
Trimercurous  Dinitrate 


Mercuric  Nitrate  Hg  -  OfN2  04  .  2ff2  0, 

Dimercuric  Nitrate  (Hg  -  0  -Hg)  =  0  2=JV2  04  .  2ff2  0, 

Trimercuric  Nitrate  (Hg-Q-Hg-0  -Hg)  =  02=N2  04.IT20. 

A  solution  of  mercurous  nitrate  with  caustic  soda  gives  a 
black  precipitate  of  mercurous  oxide. 


2Na-0-ff+  Aq)  = 
Iffg*]  0  +  (2Na-0-N02  +  ff20  +  Aq).  [303J 

A  solution  of  mercuric  nitrate  with  caustic  soda  gives  a  yel- 
low precipitate  of  mercuric  oxide. 


Aq).  [304] 

Mercurous  nitrate,  if  heated,  is  converted  into  the  red  crys-^ 
talline  variety  of  mercuric  oxide. 


=  02=N2  Oi  =  2ffffO  +  2N02.  [305] 

272.   Sulphates.  —  When  mercury  is  gently  heated  with  an  ex- 
cess of  strong  sulphuric  acid,  Mercurous  Sulphate, 


334  MERCURY.  [§  273. 

is  formed;  but  if  the  heat  be  increased,  and  the  evaporation 
carried  to  dry  ness,  the  first  product  is  changed  into  Mercuric 
Sulphate,  ffg  =  02=S02,  which  is  a  white  crystalline  powderr 
readily  dissolving  in  a  solution  of  common  salt,  but  decomposed 
by  pure  water  into  a  soluble  acid  and  an  insoluble  basic  salt. 
The  last  is  known  as  turpeth-mineraL  It  has  a  yellow  color, 
and  its  composition  is  expressed  by  the  symbol, 


Mercurous  sulphate  is  also  prepared  for  the  manufacture  of 
calomel  by  triturating  together  mercuric  sulphate  with  a  quan- 
tity of  mercury  equal  to  that  which  it  already  contains. 

273.  Sulphides.  —  Mercurous   Sulphide,    [Hg^\S,  obtained 
as  a  black  precipitate  on  passing  ff2S  gas  through  the  solution 
of  a  mercurous  salt.     Very  unstable,  like  the  corresponding  ox- 
ide.    Mercuric  Sulphide  (Vermilion,  Cinnabar),  HgS,  is  pre- 
cipitated by  the  same  reagent  from  the  solution  of  a  mercuric 
salt.     This  precipitate  is  also  black,  but  when  sublimed  the  sub- 
stance acquires  the  peculiar  vermilion  tint.  Vermilion  is  usually 
prepared  by  rubbing  together  mercury  and  sulphur,  and  sub- 
liming the  black  product.  Crystals  are  frequently  thus  obtained 
identical  in  form  with  those  of  natural  cinnabar  (76). 

274.  Chlorides.  —  Mercurous  Chloride,  \_Hg%~\  C12,  may  be 
obtained  either  as  a  white  powder  or  in  crystals  (75),  —  1st. 
By  subliming  a  mixture  of  mercuric  chloride  and  mercury, 


Hg  C12  +  Hg  =  \Hg^  C12.  [306] 

2d.  By  subliming  a  mixture  of  mercurous  sulphate  and  com- 
mon salt, 


=  Na2S04  +  [Zfo]  C12.    [307] 
3d.  By  precipitation  from  a  solution  of  mercurous  nitrate, 

([ffffdNtO,  +  2NaCl  +  Ag)  = 

C^,]  C12  +  (2NaN03  +  Aq).  [308] 

Calomel  is  insoluble  in  water,  alcohol,  and  ether.  The  Sp. 
Gr.  of  its  vapor  is  only  one  half  of  that  which  the  theory  would 
require,  —  an  anomaly  which  is  explained  as  an  effect  of  disas- 


§276.]  MERCURY.  335 

sociation.  Sublimes  below  a  red  heat  without  melting.  When 
triturated  with  a  solution  of  soda  or  potash,  it"  is  turned  black, 
owing  to  the  formation  of  (ffy2)  0,  and  when  heated  with  alka- 
line chlorides  it  is  converted  into  HgClz.  In  the  presence  of  or- 
ganic matter,  acids,  and  air,  this  last  change  may  take  place,  to 
some  extent  at  least,  at  a  temperature  of  38°  or  40°.  Calomel 
is  an  invaluable  medicine.  It  was  first  prepared  by  rubbing 
together  in  a  mortar  Hg  -f-  Hg  C12,  but  this  product,  although 
having  all  the  medicinal  properties  of  the  white  sublimate,  had 
a  brilliant  black  color,  whence  the  name,  from  Ka\bs  p.t\as. 

275.  Mercuric   Chloride  (Corrosive  Sublimate).    ffgCl2. — 
Crystalline  (77)  white  solid,  melting  at  265°,  boiling  at  293°, 
and  yielding  a  vapor  whose  Sp.  Gr.  (141.5)  conforms  very 
nearly  to  the  theory.     Soluble  in  water,  alcohol,  and  ether. 
Forms  salts  with  the  alkaline  chlorides  as  %Na  Cl .  Hg  C12.   May 
be  prepared  by  subliming  a  mixture  of  mercuric  sulphate  and 
common  salt,  but  adding  a  small  amount  of  Mn02  to  the  mix- 
ture to  prevent  the  formation  of  calomel.     Also  found  when 
mercury  is  burnt  in  chlorine  gas.     Coagulates  albumen,  and 
forms  with  it,  as  well  as  with  other  albuminoid  substances,  sta- 
ble compounds  insoluble  in  water.     Acts  as  a  violent  poison. 
Used  for  preserving  from  decay  wood,  dried  plants,  and  other 
objects  of  natural  history,  and  this  effect  appears  to  be  due  in 
part  to  its  peculiar  action  on  albuminoid  compounds.     It  is  also 
a  valuable  reagent,  and  is  used  to  prepare  other  anhydrous 
chlorides. 

Mercury  forms,  like  copper,  a  large  number  of  oxichlorides. 
It  also  combines  with  the  other  members  of  the  chlorine  group 
of  elements.  Among  these  compounds  the  most  interesting  is 
the  iodide,  Hgl^  which  affects  two  different  crystalline  forms  dis- 
tinguished also  by  striking  differences  of  color.  As  obtained 
by  precipitation 

(Hg  (74  +  2KI+  Aq)  =  HgI2  +  (2  KCl  +  Aq),     [309] 

it  appears  as  a  crystalline  red  powder  (75).  This  when 
heated  changes  its  crystalline  condition  (77)  and  becomes  yellow, 
but  the  yellow  variety  is  changed  back  to  the  red  by  mere 
friction. 

276.  Ammoniated  Compounds.  —  The  compounds  of  mer- 


336  MEECUKY.  [§277. 

cury,  when  acted  on  by  ammonia  or  its  salts,  yield  a  large  num- 
ber of  complex  products.  Among  these  the  most  remarkable 
is  a  powerful  base  called  Mercuramine,  which  is  formed  by  the 
action  of  aqua  ammonia  upon  yellow  precipitated  oxide  of  mer- 
cury. There  is  a  difference  of  opinion  in  regard  to  the  arrange- 
ment of  the  atoms  in  this  compound,  but  the  most  probable 

symbol  is  (Hg,(HgOH),H^N)-Q-H.  ff20.  The  hydrate  ab- 
sorbs O02  from  the  air,  and  forms  definite  salts  with  all  the 
common  acids.  This  compound  is  unstable,  but  when  heated, 
two  molecules  of  the  hydrate  give  up  three  molecules  of  water, 
and  there  is  left  a  dark  brown  product  permanent  in  the  air, 
whose  symbol  may  be  represented  after  the  type  \_H^N^Z0. 
The  following  are  the  symbols  of  a  few  only  of  the  many  mer- 
curial compounds  of  this  class  :  — 

formed  by  the  action  of  ammonia  gas  on  pre- 
cipitated calomel. 
black  compound,  formed  from  calomel  by 

action  of  aqua  ammonia. 
=  C^  "White  Precipitate,"  formed  by  adding 

to  aqua  ammonia  a  soluti 
Clto  "Soluble  White  Precipitate. 


277.  Characteristic  Reactions  and  Uses.  —  The  salts  of  mer- 
cury, whether  soluble  or  insoluble,  are  all  reduced  to  the  metal- 
lic state  by  a  solution  of  stannous  chloride.  Any  of  the  salts 
heated  in  a  closed  tube  with  sodic  carbonate  give  a  sublimate  of 
minute  globules  of  mercury.  From  solutions  of  its  salts  mer- 
cury is  deposited  as  a  gray  film  on  metallic  copper,  and  if  short 
lengths  of  copper  wire  thus  coated  and  carefully  dried  be  heated 
in  a  closed  tube,  the  sublimate  is  obtained  as  before. 

The  chief  consumption  of  metallic  mercury  is  in  the  treat- 
ment of  gold  ores.  It  is  also  used  for  silvering  mirrors,  for 
making  various  philosophical  instruments,  and  for  other  pur- 
poses in  the  arts.  Large  quantities  are  consumed  in  prepar- 
ing its  various  compounds,  and  these  are  among  the  most  im- 
portant articles  of  the  materia  medica. 


QUESTIONS  AND  PROBLEMS.  337 

Questions  and  Problems. 

1.  Write  the  reaction  of  boiling  sulphuric  acid  on  copper. 

2.  Write  the  reaction  of  nitric  acid  on  copper,  —  1st,  assuming 
that  NO  is  the  aeriform  product ;  2d,  that  it  is  NZ0. 

3.  Write  the  reaction  which  takes  place  when  cupric  nitrate  is 
decomposed  by  heat. 

4.  Why  does  not  concentrated  nitric  acid  act  on  copper  ? 

5.  Represent  the  constitution  of  the  hydrate  4[Cw0]0  .  HZ0  in  the 
typical  form.     How  may  it  be  regarded  as  related  to  the  normal 
hydrate  [CwJ=flb,  ?  Ans.  It  equals  4[Cw2>#oa  —  3#20. 

6.  How  may  anhydrous  cupric  sulphate  be  used  to  detect  the 
presence  of  moisture  ? 

7.  In  what  other  way  may  the  symbols  of  the  different  basic  sul- 
phates be  written  ? 

Ans.  The  symbol  of  Brochantite  may  be  written  (Cu-O-Cu-0- 
Cu-0-Cu)=02=S02.  BH20,  and  the  others  in  a  similar  way. 

8.  How  may  the  symbols  of  the  basic  sulphates  be  derived  from  the 
hydrates  ? 

Ans.  Disregarding  the  water  of  crystallization,  we  may  regard  Bro- 
chantite  as  formed  from  the  condensed  hydrate  4Cu=02=Hz 
by  first  eliminating  3HZO  and  then  replacing  the  remaining 
H2  by  SOy 

9.  If  the  symbol  of  Brochantite  is  written  as  in  the  text,  to  what 
order  of  sulphates  does  it  belong  ?  Ans.  Orthosulphates. 

10.  Show  by  graphic  symbols  that  the  radical  Cu  0ZH  must  be  a 
monad. 

11.  Represent  by  graphic  symbols  the  composition  of  Malachite 
and  Azurite. 

12.  Both  Malachite  and  Azurite  may  be  regarded  as  formed  by 
the  molecular  union  of  cupric  hydrate  and  cupric  carbonate.     Write 
the  symbols  on  this  theory. 

13.  Malachite  is  how  related  to  cupric  hydrate? 

Ans.  It  may  be  regarded  as  the  hydrate  doubly  condensed  with  two 
of  the  hydrogen  atoms  replaced  by  CO  thus,  Cu,=OfCO,tf3 
or  Cu-O^CO .  Cu-OfH$.  Symbol  of  Azurite  in  the  same 
way  becomes  Cu,W^(CO\,H3  or  2Cu=02=CO.  Cu=OfHf 

14.  To  what  order  of  carbonates  does  Mysorin  belong? 

15  V 


338  QUESTIONS  AND  PKOBLEMS. 

15.  In  what  other  ways  may  the  symbol  of  the  cupric  nitrates  be 
written  ? 

Ans.  Cu=Of(NOa\  and  Cu=0=NO^Hy  or  Cu=Of(NO^,H  .  Cu* 


16.   Write  the  symbol  of  dioptase  in  the  same  typical  form. 

Ans.  Hz,Cu=OfSL 

1  7.   To  what  order  of  silicates  may  dioptase  be  referred  ? 

Ans.  Orthosilicates. 

18.  Write  the  reaction  of  solution  of  sodic  phosphate  on  solution 
of  cupric  sulphate. 

19.  Represent  the  constitution  of  the  various  sulphides  of  copper 
by  graphic  symbols. 

20.  In  what  relation  does  the  fluohydrate  of  copper  stand  to  the 
hydrate  and  fluoride  of  the  same  metal  ? 

Ans.  It  holds  an  intermediate  position,  as  shown  by  the  symbols 
Cu=Hoz,  Cu=Ho,Fl,  CuFlz. 

21.  Regarding  the  molecule  of  water  in  the  common  variety  of 
Atacamite  as  water  of  constitution,  how  may  the  formula  of  this 
mineral  be  simplified  ? 

Ans.  It  may  be  halved  and  written  (Cu-0-Cu)=Ho,CL 

22.  How  is  Atacamite  related  to  cupric  hydrate  ? 

Ans.  2Cu=Ho2  =  (Cu-0-Cu)=Ho2  -\-  H20,  then  replacing  one 
atom  of  Ho  in  basic  hydrate  by  CL 

23.  What  do  you  find  that  is  remarkable  in  the  reaction  of  cupric 
hydride  on  hydrochloric  acid  ?     Compare  it  with  reaction  [236],  and 
consider  whether  it  indicates  a  difference  of  condition  in  hydrogen 
similar  to  that  in  oxygen. 

24.  Write  the  symbols  of  the  ammonia  compounds  of  copper  in 
the  vertical  form. 

25.  What  evidence  can  you  find  that  a  portion  of  the  nitrogen 
atoms  in  two  of  the  compounds  stand  in  a  different  relation  to  the 
molecule  from  the  others  ? 

Ans.  If  the  nitrogen  atoms  were  all  typical,  we  should  expect  the 
basic  radicals  to  fix  more  than  the  equivalent  of  two  univa- 
lent  acid  radicals. 

26.  Write  the  symbols  of  the  hydrates  which  correspond  to  the 
different  basic  nitrates  of  mercury,  and  show  how  such  basic  hy- 
drates may  be  derived  from  the  assumed  normal  hydrates. 

27.  How  is  it  possible  that  salts  should  exist  corresponding  to  hy- 
drates that  cannot  be  isolated  ? 


QUESTIONS  AND  PKOBLEMS.  339 

28.  Show  how  turpeth-mineral  may  be  derived  from  an  assumed 
normal  hydrate. 

29.  How  would  you  seek  to  determine  whether  the  black  product 
obtained  by  grinding  together  Hg  -j-  S  is  a  mixture  or  a  compound  ? 

30.  By  experiment  it  appears  that  the  specific  gravity  of  calomel 
vapor  is  118.5.     What  should  it  be  theoretically?     Into  what  is  it 
probably  decomposed  when  heated  ?        Ans.  235.5 ;  Hg  and  HgCl^. 

31.  In  administering  calomel  as  medicine,  what  associations  with 
other  drugs  should  be  avoided  ? 

32.  How  may  calomel  be  distinguished  from  corrosive  sublimate  ? 

33.  What  is  the  theoretical  Sp.  Gr.  of  HgCly  and  why  should  you 
anticipate  so  great  a  difference  between  it  and  the  experimental  re- 
sult? 

Ans.  135.5.     In  such  a  dense  vapor  the  deviation  from  Mariotte's 
law  would  probably  be  large. 

34.  Write  the  reaction  which  takes  place  when  a  mixture  of  mer- 
curic sulphate  and  common  salt  are  sublimed. 

35.  In  cases  of  poisoning  by  corrosive  sublimate,  why  should  milk 
or  the  white  of  eggs  be  useful  as  temporary  antidotes  until  the  stomach 
can  be  emptied  by  an  emetic  or  otherwise  ? 

36.  Write  the  symbols  of  the  chloride,  nitrate,  sulphate,  and  car- 
bonate of  mercuramine. 

37.  Write  the  symbol  of  the  oxide  of  mercuramine  described 
above. 

38.  Represent  the  different  ammoniated  compounds  of  mercury 
by  vertical  symbols,  and  point  out  the  type  of  each. 


340  CALCIUM.  §278.] 


Division  V. 

278.  CALCIUM.  Oa  —  40.  —  Dyad.      One  of  the  most 
abundant  and  important  constituents  of  the  crust  of  the  globe. 
The  elementary  substance  is  a  soft,  malleable  metal,  with  a 
reddish  tinge  of  color.     Readily  tarnishes  in  the  air,  and  burns 
when  heated,  forming  lime.     Decomposes  water  at  all  temper- 
atures, forming  calcic  hydrate. 

The  metal  is  obtained  with  difficulty  either  by  the  electroly- 
sis of  the  melted  chloride  or  by  decomposing  the  iodide  with 
sodium. 

279.  Calcic  Carbonate.   Co,  =  0.2=  CO  or  Cao  =  CO.  —  The  chief 
lime  mineral.     Remarkable  for  the  great  variety  of  its  crystal- 
line forms.    Dimorphous  (Hexagonal  and  Orthorhombic).    The 
hexagonal  forms  (Figs.  14,  16,  17,  40,  41,  and  42)  belong  to 
the  mineral  species  Calcite.     The  orthorhombic  forms  (74)  to 
the  species  Aragonite.     Sp.  Gr.  of  Calcite  2.72,  of  Aragonite 
2.94.     The  last  is  also  distinguished  from  the  first  by  superior 
hardness,  and  falling  to  powder  when  heated.     The  crystalline 
varieties  of  calcite  are  readily  recognized  by  a  very  striking 
rhombohedral  cleavage.     Limestones,  Oolite,  Chalk,  Marble, 
Travertine,  Tufa,  Calcareous  Marl,  are  names  of  varieties  of 
rocks,  which  consist  chiefly  or  wholly  of  one  or  the  other  of 
these  two  minerals,  generally  of  calcite.     Many  of  these  rocks 
make  excellent  building  stones.      All  the  varieties  of  calcic 
carbonate  dissolve  with  effervescence  in  dilute  nitric  and  other 
acids,  and  may  thus  be  distinguished  from  the  siliceous  miner- 
als which  they  sometimes  outwardly  resemble.    Calcic  carbonate, 
although  nearly  insoluble  in  pure  water,  is  readily  dissolved  by 
water  charged  with  C02.  Thus  it  is  held  in  solution  by  the  water 
of  lime  districts,  and  to  a  greater  or  less  extent  by  most  spring 
water.     Such  water,  when  strongly  charged,  deposits  calcic  car- 
bonate on  exposure  to  the  air,  and  thus  are  formed  stalactites, 
tufa,  and  travertine.     It  also  forms  deposits  in  boilers,  and  de- 
composes the  soap  used  in  washing.     (Hard  water.)      Calcic 
carbonate  may  be  readily  formed  artificially  by  the  reaction 


§  282.]  CALCIUM.  341 


(OaCl2  +  (Nff,)2=C03  +  Aq)  = 

Ca-C03  +  (2(Nff4)  Cl  +  Ag).  [311] 

Singularly,  however,  if  the  products  of  the  reaction  are  boiled 
together,  the  reverse  change  takes  place  ;  calcic  chloride  is 
formed,  which  dissolves,  while  ammonic  carbonate  is  carried 
away  with  the  steam. 

280.    Calcic  Oxide  (  Quick-lime).  Ca  0.  —  Obtained  by  burn- 
ing limestone  in  kilns. 


Ca  CO3  =  CaO  +  @©2.  [312] 

Amorphous  white  solid.  Very  infusible,  and  emitting  an  intense 
white  light  when  ignited  (Drummond  Light).  Has  strong  af- 
finity for  water,  and  the  chemical  union  is  attended  with  the 
evolution  of  much  heat  (slaking).  Exposed  to  the  air,  it  grad- 
ually absorbs  both  water  and  carbonic  anhydride  (air  slaking). 

281.  Calcic  Hydrate.   Ca=Ho2.     A  light  dry  powder.     Sol- 
uble in  about  425  parts  of  cold  water  (lime-water).     With  a 
smaller  quantity  of  water  it  forms  a  sort  of  emulsion  called 
milk  of  lime,  and  with  still  less  water  it  gives  a  somewhat 
plastic   paste,   which,  mixed   with    sand,  is   ordinary  mortar. 
Hydraulic  cements,,  which  harden  under  water,  are  made  from 
limestones   containing  from  fifteen  to  thirty-five  per  cent  of 
finely  divided  silica  or  clay  ;  also  by  intimately  mixing  with 
chalk  a  due  proportion  of  clay  under  regulated  conditions,  and 
subsequently  burning.     Calcic  hydrate  acts  on  the  skin  like  a 
caustic  alkali,  and  is  used  by  the  tanners  for  removing  hair 
from  hides.     It  has  a  strong  affinity  for  CO*  and  hence  is  used 
for  rendering  soda  and  potash  caustic  [97].     It  is  also  em- 
ployed for  purifying  coal-gas,  and  in  many  other  processes  of 
the  arts.     It  is  largely  used  as  a  manure.     Whitewash  is  milk 
of  lime  mixed  with  a  little  glue. 

282.  Chloride  of  Lime  or  Bleaching   Powder,   CaOCl2,   is 
formed  by  passing  chlorine  gas  into  leaden  chambers  containing 
slaked  lime,  which  absorbs  the  gas  very  rapidly. 

Ca  0  +  Cl-  Cl=(Ca-  0)-  C12.  [313] 

Very  much  used  in  the  arts  for  bleaching  cotton  goods.  The 
cloth  having  been  well  washed  and  digested  in  a  weak  solution 


342  CALCIUM.  [§283. 

of  chloride  of  lime,  is  passed  into  very  dilute  sulphuric  acid, 
which  liberates  the  chlorine  in  the  fibre  of  the  cloth.  May  also 
be  used  in  the  laboratory  r,s  a  source  of  chlorine  gas. 


(CaOClz  +  Jf2S04  +  Aq)  = 

t  +  ff20  -t-  Aq)  +  01-01.  [314] 


283.  Calcic  Peroxide.     (Ca-0)=0.  —  Formed  by  adding 
to  lime-water,  but  is  a  very  unstable  compound. 

284.  Calcic  Sulphate.   Ca  =  02=S02.  —  Second  in  importance 
of  the  lime  minerals.     It  occurs  in  nature  both  in  an  anhydrous 
and  hydrous  form.     The  anhydrous  mineral  is  called  Anhydrite, 
the  hydrous  mineral  is  Gypsum.     Anhydrite  crystallizes  in  the 
orthorhombic  system  (77),  and  has  Sp.  Gr.  =  2.9.     Gypsum 
(CaS04  .  2ff20)  crystallizes  in  the  monoclinic  system  (Fig.  25), 
has  Sp.  Gr.  =  2.3,  and  is  softer  than  the  first.     Calcic  sulphate 
is  soluble  in  about  400  parts  of  water,  and,  like  several  of  the 
lime  salts,  is  much  less  soluble  in  hot  water  than  in  cold  ;  and 
when  water  holding  gypsum  in  solution  is  heated  to  a  high  tem- 
•perature  in  steam-boilers,  the  whole  is  deposited  in  an  insoluble 
condition    (CaS04.  \H^G).     It  is  a  very  common  impurity 
of  spring  waters,  and  is  another  cause  of  their  hardness,  and  of 
the  crusts  which  they  sometimes  form  on  the  inner  surface 
of  boilers.     It  is  found  in  considerable  quantity  in  the  water  of 
salt  springs,  and  of  the  ocean.      When  these  waters  are  evap- 
orated it  is  deposited  before  the  common  salt.     Hence  in  nature 
we  find  that  beds  of  rock-salt  are  usually  associated  with  anhy- 
drite and  gypsum.     The  last  is  by  far  the  most  abundant  min- 
eral, forming  in  some  places  extensive  rock  deposits  of  great 
thickness.      It  is,  moreover,  found  in  beautifully  transparent 
crystals  (Selenite),  which  can  be  easily  split  into  very  thin 
plates,  and  it  also  forms  the  ornamental  stone  called  alabaster. 
When  heated,  gypsum  readily  gives  up  its  water  of  crystalliza- 
tion, and  when  not  overburnt  the  dry  product,  if  reduced  to 
powder  and  made  into  a  paste,  again  unites  with  water  and  sets 
into  a  hard  mass.     This  reunion,  however,  will  not  take  place 
if  the  gypsum  has  been  heated  above  300°  ;  and  anhydrite  is 
then  formed.     The  calcined  gypsum,  called  Plaster  of  Paris,  is 
used  in  immense  quantities  for  making  casts,  and  in  various 
forms  of  stucco-work.     Ground  gypsum  is  also  a  valuable  ma- 
nure, and  finds  other  applications  in  the  arts. 


§288.]  CALCIUM.  343 

285.  Calcic  Phosphate.   Cao3(PO)2.  —  The  chief  earthy  con- 
stituent of  the  bones  of  animals.     The  animal  obtains  it  from 
the  plants,  and  the  plant  draws  its  supply  from  the  soil.     The 
.grains  of  the  cereals  are  especially  rich  in  this  bone-making 
material,  and  as  the  supply  in  the  soil  is  usually  limited,  these 
plants,  when  cultivated  year  after  year,  soon  exhaust  it.    Hence 
it  is  all  important  for  the  agriculturist  to  restore  to  his  land  the 
phosphates  as  fast  as  they  are  removed  by  the  crops,  and  ground 
bones,  guano,  phosphorite,  and  other  forms  of  calcic  phosphate, 
are  used  for  this  purpose.     The  mineral  Apatite  is  a  crystal- 
line variety  (Fig.  14)  of  this  same  material,  but  contains  also 
about  eight  per  cent  of  calcic  fluoride  mixed  with  more  or  less 
calcic  chloride.    Its  symbol  may  be  written  (Ca5F)ixOQix(PO)s. 

286.  Calcic  Silicate  (Tabular  Spar),  Cao=SiO,  is  a  not  un- 
common mineral.     Formed  on  the  surface  of  the  grains  of  sand 
when  mortar  hardens ;  and  the  valuable  qualities  of  hydraulic 
cements  are  probably  due  to  a  still  more  complete  union  of  the 
same  kind.     An  artificial  stgne  of  great  strength  may  be  made 
by  first  mixing  together  solutions  of  calcic  chloride  and  sodic 
silicate,  and  then  incorporating  with  the  half-fluid  mass  a  large 
proportion  of  sand. 

287.  Calcic  Fluoride  (Fluor- Spar).   CaF2.  —  An  abundant 
mineral  and  the  most  important  compound  of  fluorine.     It  is 
found  both  massive  arid  crystallized  in  the  forms  of  the  isomet- 
ric system,  generally  in  cubes.     Has  octohedral  cleavage.     The 
pure  material  is  colorless,  but  the  native  crystals  are  frequently 
beautifully  colored,  and  are  among  the  most  splendid  specimens 
of  our  mineral  cabinets.     Exposed  to  the  light,  they  frequently 
exhibit  a  remarkable  fluorescence,  and  many  varieties  of  the 
mineral  phosphoresce  when  heated.    Although  not  very  fusible 
by  itself,  fluor-spar  forms  a  very  fusible  slag  with  gypsum  and 
other   earthy  minerals   frequently  associated  with  lead  ores. 
This  property  renders  it  a  valuable  flux  in  the  process  of  smelt- 
ing such  ores,  and  hence  the  name  fluor.     In  small  quantities  it 
is  almost  invariably  associated  with  calcic  phosphate,  not  only 
in  the  mineral  kingdom,  but  also  in  the  bones  and  teeth  of 
animals. 

288.  Calcic  Chloride.   CaCl2.  —  A  deliquescent  salt,  readily 
obtained  by  dissolving  calcic   carbonate  in  hydrochloric  acid. 
Also  a  secondary  product  in  the  preparation  of  ammonia  [162]. 


344  STRONTIUM.  —  BARIUM.  [§289. 

OaO03  +  (2HOI  +  Aq)  = 

(CaCl2  -\-ff20  +  Aq)  +  C02.  [315] 


A  useful  reagent,  and  also  employed,  on  account  of  its  hygro- 
scopic qualities,  for  drying  gases. 

289.  Calcic  Nitrate.    Cao=(N02)2.  —  Also   a  very  soluble 
deliquescent  salt,  which  is  formed  in  the  soil,  in  cellars,  in  lime 
caverns,  and  wherever  organic  matter  decays  in  contact  with 
calcareous  materials.    Chiefly  important  as  a  source  of  saltpetre. 

290.  STRONTIUM,  Sr=87.6,  and  BARIUM,  Ba  =  l37. 
—  Dyads.     The  compounds  of  these  elements  are  closely  allied 
to  the  corresponding  compounds  of  calcium,  and  the  differences 
are  only  those  which  we  should  expect  between  members  of  the 
same  chemical  series.     They  are,  however,  far  less  abundantly 
distributed  in  nature.     The  most  important  native  compounds 
are 

Strontic  Carbonate,  Strontianite,  SrC03,  Sp.  Gr.  3.70. 
Baric  Carbonate,  Witherite,  BaCOs,  Sp.  Gr.  4.32. 

These  are  isomorphous  with  Aragonite.  No  hexagonal  forms 
corresponding  to  calcite  are  known.  In  like  manner  we  have 

Strontic  Sulphate,      Celestine,  SrSO#          Sp.  Gr.  3.95. 

Baric  Sulphate,  Heavy  Spar,      BaSO^        Sp.  Gr.  4=AS. 

These  are  isomorphous  with  anhydrite.  No  hydrous  minerals 
corresponding  to  gypsum  are  known.  Strontic  sulphate  is  much 
less  soluble  in  water  than  calcic  sulphate,  and  baric  sulphate  is 
practically  insoluble.  Moreover,  the  solubility  of  these  salts  is 
not  increased  by  the  presence  of  weak  acids.  Hence  a  solution 
of  calcic  sulphate  will  give  a  precipitate  in  solutions  containing 
either  strontium  or  barium,  and  a  solution  of  strontic  sulphate 
only  in  the  last.  The  sulphates  are  both  easily  prepared  artifi- 
cially from  solutions  of  corresponding  chlorides  by  precipitation 
with  sulphuric  acid. 

291.  The  Strontic  and  Baric  Nitrates  and  the  Strontic  and 
Baric  Chlorides  are  all  soluble  salts,  but  less  soluble  than  the 
corresponding  salts  of  calcium,  the  barium  compounds  being  in 
each  case  the  less  soluble  of  the  two.     They  are  easily  prepared 
by  dissolving  the  native  carbonates  in  dilute  nitric  or  hydro- 


§295.]  STRONTIUM.  —  BARIUM.  345 

chloric  acids.  Baric  nitrate  is  precipitated  from  its  aqueous 
solution  by  strong  nitric  or  hydrochloric  acid  in  consequence  of 
its  sparing  solubility  in  these  reagents.  They  may  also  be  pre- 
pared from  the  native  sulphates,  as  is  illustrated  by  the  follow- 
ing reactions  :  — 

SrS04  +  4(7=  SrS+  4®©. 

[316] 
(SrS  +  ZHCl  +  Aq)  =  (SrOl2  +  Aq)  +  SL^. 

An  intimate  mixture  of  the  powdered  sulphate  with  some  car- 
bonaceous material  is  first  intensely  heated  in  a  crucible.  The 
resulting  product  is  then  exhausted  with  water,  and  the  solution 
treated  with  hydrochloric  or  nitric  acid  as  required. 

292.  Strontic  and  Baric  Hydrates  may  also  be  prepared 
from  the  solution  of  the  sulphides,  obtained  as  above,  by  the 
reaction 


(BaS  +  H,0  +  Aq)  = 

CuS+(Ba=ffo2+Aq).  [317] 

The  relative  solubility  of  the  hydrates  follows  the  inverse  order 
of  that  of  the  other  salts,  baric  hydrate  being  much  the  most  sol- 
uble and  dissolving  in  twenty  parts  of  water. 

293.  Strontic  and  Baric  Oxides  may  be  readily  obtained  by 
igniting  the  nitrates.     They  slake  when  mixed  with  water,  like 
quick-lime. 

294.  Strontic  and  Baric  Peroxides  are  prepared  by  heating 
the  oxides  in  an  atmosphere  of  oxygen  gas.     They  are  more 
stable  than  calcic  peroxide,  and  baric  peroxide  is  an  important 
reagent. 

295.  Characteristic  Reactions.  —  Calcium,  strontium,  and 
barium  are  all  precipitated  from  their  solutions  by  alkaline  car- 
bonates and  by  oxalic  acid.     They  may  be  distinguished  from 
each  other  by  the  relative  solubility  of  their  sulphates,1  and  by 
the  colors  of  their  flames,  which  show  characteristic  bands  with 
the  spectroscope.     The  compounds  of  strontium  impart  to  a 
colorless  flame  a  brilliant  crimson  color,  and  those  of  barium  a 

1  Calcic  sulphate  gives  an  instantaneous  precipitate  in  solutions  of  barium 
salts,  while  in  those  of  strontium  the  precipitate  only  forms  after  a  perceptible 
interval  of  time. 

15* 


346  LEAD.  [§296. 

yellowish  green.  Hence  they  are  much  used  by  makers  of  fire- 
works. The  soluble  salts  of  barium  are  important  reagents  in 
the  laboratory,  and  both  the  native  and  the  artificial  sulphate 
furnish  an  important  white  paint. 

296.  LEAD.  Pb  =  207.     Bivalent  or  quadrivalent.     One 
of  the  more  abundant  metallic  elements,  found  chiefly  in  mineral 
veins.     Principal  ore  is  Galena,  PbS.     There  is  also  a  native 
Plumbic   Carbonate  called   Cerusite   (PbC03,  Sp.  Gr.  6.48), 
isomorphous  with  Aragonite,  and  a  native  Plumbic  Sulphate 
called  Anglesite  (PbSO#  Sp.  Gr.  6.30),  isomorphous  with  an- 
hydrite. 

297.  Metallic  Lead.  Pb?—Sp.  Gr.  11.36.      Melting-point, 
325°.     So  soft  that  it  can  be  moulded  by  pressure.     Obtained, 
1st.  By  alternately  roasting  and  melting  the  galena  in  a  rever- 
beratory  furnace. 

Roasting  stage, 

30=0  =  PbS      ZPbO       2^(fi>   or 


20=0  =  PbS  +  PbS04-, 


Melting  stage,  PbS  +  2PbO  =  3Pb  +  ^©2,  or 
PbS+  PbSO*  = 


2d.     By  smelting  the  galena  with  scrap-iron  in  a  blast-furnace, 
PbS  +  Fe  =  FeS  +  Pb.  [320] 

Practically,  nowever,  both  processes  are  far  more  complex  than 
the  reactions  would  indicate.  The  ore  is  in  all  cases  mixed  with 
gangue,  which  can  only  be  melted  with  the  aid  of  some  flux, 
and  the  slags  thus  formed  contain  a  large  amount  of  metal  and 
must  be  smelted  again. 

Lead  dissolves  readily  in  dilute  nitric  acid,  but  is  not  acted 
on,  or  only  very  slightly,  by  either  hydrochloric  or  sulphuric 
acids,  unless  concentrated  and  boiling.  Employed  in  number- 
less ways  in  the  arts,  both  pure  and  alloyed,  with  other  metals. 
Type-metal,  britannia-metal,  and  solder  are  among  the  most  im- 
portant of  its  alloys. 

298.  Plumbic  Oxide.  PbO.  —  Obtained  by  heating  tead  in  a 
current  of  air,  when,  if  the  heat  is  not  too  great,  a  yellow  pow- 
der is  obtained  called  Massicot.  At  a  heat  a  little  below  red- 


§302.]  LEAD.  347 

ness  the  oxide  melts  and  crystallizes  on  cooling  in  yellowish 
red  scales  called  Litharge.  Largely  used  in  the  arts  for  mak- 
ing flint-glass,  for  glazing  earthenware,  and  for  preparing  vari- 
ous paints  and  lead  salts. 

299.  Plumbic  Peroxide.   Pb02.  —  A   dark-brown    powder, 
very  useful  in  the  laboratory  as  an  oxidizing  agent.     The  bright 
red  powder  called  Minium,  obtained  by  still  further  roasting 
massicot  at  a  low  red  heat,  is  a  mixture  of  Pb02  and  PbO. 
There  is  also  a  suboxide,  Pb20. 

300.  Plumbic  Hydrate.  —  The  normal  hydrate,  Pb=Ho^  has 
never  been  obtained,  but  we  can  readily  form 

Diplumbic  Hydrate  (Pb-0-Pb)=ffo2, 

Triplumbic  Hydrate  (Pb-0-Pb-0-Pb)-Hb^ 

by  the  following  reactions  :  — 

2Pb=(N03)2  +  (\K-Ho  +  Aq)  = 

(Pb-0-Pb)-Ho2  +  (±K-NOs  +  ff20  +  Aq).  [321] 


((Pb302)-(C2ff302)2 

(Pb302)-ffo2  -f  (2(NHt)-(C2Hs02)  +  Aq).  [322] 


A  plumbic  hydrate  is  formed  by  the  simultaneous  action  of 
air  and  water  on  lead,  which  is  slightly  soluble  ;  and  as  all  lead 
salts  are  poisonous,  and  even  in  minute  quantities,  if  the  dose  is 
often  repeated,  may  be  injurious  to  health,  it  is  not  safe  to  use, 
for  drinking,  water  which  has  been  kept  in  cisterns  lined  with 
lead  or  drawn  through  lead  pipes.  The  presence  of  nitrites, 
nitrates,  or  chlorides  greatly  increases  the  corrosive  action  of 
water  on  lead,  while  carbonates  and  sulphates  exert  a  preser- 
vative influence. 

301.  Plumbic  Nitrate.  Pb=(NOs)2.  —  Obtained  by  dissolving 
litharge  or  lead  in  dilute  nitric  acid..  Soluble  in  water,  but  in- 
soluble in  strong  nitric  acid. 

PbO+  (2ff-N03  +  Aq)  =  (Pb=(N03)2+ff20+Aq).  [323] 


(SH-N03  +  Aq)  = 

(3Pb-(N03)2  +  ±H.20  +  Aq)  +  23BST®.  [324] 

302.    Plumbic   Acetate    (Suyar   of  Lead). 


848  LEAD.  [§303. 

Sff20. —  The  most  important  soluble  salt  of  lead,  easily  ob- 
tained by  dissolving  PbO  in  acetic  acid.  Lead  has  a  great 
tendency  to  form  basic  salts  (38).  Hence  a  solution  of  the 
neutral  acetate  will  dissolve  a  large  additional  quantity  of 
litharge. 

2PbO  +  (Pb=(C2ff302)2-}-  Aq)  = 

'  ((Pb-0-Pb-0-Pb)=(C2ff302),+  Aq).  [325] 

If  O02  is  now  passed  through  this  solution,  the  excess  of  PbO 
is  precipitated  as  carbonate.  Fresh  portions  of  Pb  0  may  then 
be  dissolved  and  the  process  repeated.  The  plumbic  carbonate, 
which  is  obtained  by  this  and  other  analogous  methods,  is  very 
much  used  as  a  white  paint  under  the  name  of  white  lead.  The 
products  of  the  different  processes  have  not,  however,  the  same 
composition,  but  are  mixtures  of  the  carbonate  and  hydrate  in 
varying  proportions. 

303.  Plumbic  Sulphate,  PbS04,  is  obtained  as  a  white  pre- 
cipitate on  adding  sulphuric  acid  or  a  soluble  sulphate  to  a  solu- 
tion of  a  salt  of  lead.     It  is  practically  insoluble  in  pure  water 
and  dilute  sulphuric  acid. 

304.  Plumbic  Phosphate  is  found  in  nature  in  the  mineral 
Pyromorphite,  which  is  isomorphous  with  apatite  and  has  an 
analogous  constitution  (Pb&Cl)  i*  0Qix(PO)B.    The  mineral  Mim- 
etine  is  the  corresponding  isomorphous  arseuiate.     A  melted 
globule  of  plumbic  phosphate  assumes  on  cooling  a  peculiar 
radiated  crystalline  structure,  which  is  very  characteristic. 

305.  Plumbic  Chloride,  PbCl2,  may  be  obtained  as  a  white 
crystalline  powder  by  the  reactions 

PbO  +  (2HOI  +  Aq)  =  PbCl2  -\-(ff20  +  Aq).>  [326] 

(Pb(N03)2  +  2HOI  +  Aq)  = 

PbOl2  +  (2HN03  +  Aq).  [327] 

It  is  only  very  slightly  soluble  in  cold  water,  but  in  boiling 
water  dissolves  quite  readily. 

306.  Plumbates.  —  Caustic  alkalies  dissolve  Pb  0  very  freely, 
forming  salts  in  which  the  lead  plays  the  part  of  a  negative 
radical.     Hence  the  precipitate  formed  in  reaction  [321]  dis- 
solves /in  an  excess  of  the  reagent,  and  a  solution  of  Pb  0  in 
lime-water  is  used  as  a  hair-dye. 


§307.J        REACTIONS  AND  PROBLEMS.  349 

307.  Characteristic  Reactions.  —  The  lead  compounds,  in 
many  of  their  reactions,  are  closely  allied  to  the  compounds  of 
the  first  three  elements  of  this  group.  For  example,  the  sol- 
uble salts  give  precipitates  with  the  alkaline  carbonates  and 
with  oxalic  acid.  But  in  other  reactions  there  are  marked  dif- 
ferences. Thus,  1.  A  strip  of  metallic  zinc  placed  in  a  solution 
of  plumbic  acetate  precipitates  all  the  lead. 

Zn,  +  (Pb-(02ff302)2  +  Aq)  = 

Pb  +  (Zn=(C2ff302)2  +  Aq).  [328] 

2.  Sulphuretted  hydrogen  gas  passed  through  either  an  acid  or 
an  alkaline  solution  of  a  salt  of  lead  gives  a  black  precipitate  of 
plumbic  sulphide. 


(Pb-Cl2  +  H2S  +  Aq)  =  PbS  +  (2ffOl  +  Aq).  [329] 

When  the  solution  is  acidified  with  hydrochloric  acid,  the  pre- 
cipitate is  first  red,  owing  to  the  formation  of  (Pb-S-Pb)=Cl2, 
but  this  is  soon  converted  into  the  black  sulphide.  3.  Heated 
on  charcoal  before  the  blow-pipe,  with  reducing  fluxes,  the 
compounds  of  lead  yield  a  soft,  malleable  bead  of  metal,  and  the 
charcoal  immediately  around  the  bead  is  at  the  same  time 
coated  with  an  incrustation  of  oxide  which  is  orange-colored 
while  hot,  but  becomes  lemon-yellow  when  cold.  By  these 
reactions  lead  is  easily  distinguished  from  calcium,  strontium, 
and  barium.  Indeed,  the  distinction  is  so  marked,  that,  al- 
though the  resemblances  are  very  striking,  it  may  be  doubted 
whether  lead  belongs  to  the  same  chemical  series. 


Reactions  and  Problems. 

1.  Calcite  and  Aragonite  are  both  not  unfrequently  found  in  acic- 
ular  crystals.     How  may  they  be  distinguished  ? 

2.  Compare  the  molecular  volumes  of  Calcite  and  Aragonite. 

3.  By  igniting  100  parts  of  pure  calcic  carbonate,  Dumas  obtained 
exactly  56  parts  of  lime.     What  is  the  atomic  weight  of  calcium? 

Ans.  40. 

4.  What  assumptions  are  made  in  the  last  problem  ?     (19.) 


350  REACTIONS   AND   PROBLEMS. 

5.  How  much  Ca  0  can  be  obtained  from  1 00  kilogrammes  of  pure 
limestone  ?     How  much  Ca=Hoz  will  this  amount  yield  ? 

Ans.  56  kilos,  and  74  kilos. 

6.  How  much  limestone  must  be  burnt  to  yield  560  kilos,  of  quick- 
lime ?     How  many  cubic  metres  of  C02  would  be  set  free  in  the 
process?  Ans.  1,000  kilos,  and  223.1  m".3 

7.  In  one  cubic  metre  of  limestone  assumed  to  be  pure  calcic  car- 
bonate, Sp.  Gr.  2.72,  how  many  cubic  metres  of  COZ  are  condensed  ? 

Ans.  607.1  m:8 

8.  What  is  the  cause  of  the  incrustation  of  boilers  by  calcic  car- 
bonate ? 

9.  Lime-water  is  used  to  purify  hard  water.    Explain  the  reaction. 

10.  A  bed  of  limestone,  Sp.  Gr.  =  2.75,  and  100  metres  thick, 
would  make  a  bed  of  anthracite  coal  of  what  thickness  ?     Assume 
that  the  Sp.  Gr.  of  anthracite  is  1.8,  and  that  it  contains  90  per  cent 
of  carbon.  Ans.  20.37  metres. 

11.  In  order  to  precipitate  lime  as  completely  as  possible  with 
ammonic  carbonate,  it  is  important  to  avoid  an  excess  of  ammonia 
salts,  and  to  warm  the  liquid,  but  not  to  boil  it.     Give  the  reasons 
for  these  precautions.     Also  analyze  reactions  [311  and  the  reverse], 
and  state  the  principle  under  which  they  may  be  brought. 

12.  One  cubic  decimetre  of  quick-lime,  Sp.  Gr.  3.18,  will  absorb 
how  many  cubic  decimetres  of  water  ?     How  many  units  of  heat  will 
be  evolved  by  the  change  of  state  which  the  water  undergoes  ? 

Ans.  1.022  d^i:8 

13.  In  burning  quick-lime  it  is  found  that  the  process  succeeds 
best  in  damp  weather,  and  is  facilitated  by  injecting  steam  into  the 
kiln.     Why  should  you  infer  that  this  would  be  the  case  ?     (58.) 

14.  Give  an  explanation  of  the  hardening  and  adhesion  of  mortars 
and  cements. 

15.  When  milk  of  lime  is  spread  over  walls  in  the  process  of  white- 
washing, what  compound  is  formed  on  the  surface  ? 

16.  How  many  cubic  metres  of  C02  can  be  absorbed  by  a  quan- 
tity of  milk  of  lime,  containing  112  kilos,  of  lime  (CaO)  ? 

1 7.  When  lime-water  is  shaken  up  with  COZ  it  is  rendered  turbid. 
How  do  you  explain  the  reaction,  and  to  what  application  of  lime- 
water  in  the  laboratory  does  it  point? 

18.  In  order  to  render  100  kilos,  of  sal  soda  caustic  how  much 
quick-lime  must  be  used?     [97.]  Ans.  52.83  kilos. 

19.  How  many  litres  of  chlorine  gas  would  be  absorbed  by  100 


1  REACTIONS  AND  PROBLEMS.  351 

kilos,  of  lime  (CaO)  first  reduced  to  hydrate,  and  how  much  MnOt 
must  be  used  to  yield  the  requisite  amount  ? 
,  Ans.  in  part,  39.85  litres  of  chlorine. 

20.  Bleaching  salts  have  been  regarded  as  a  mixture  of  calcic 
chloride  with  calcic  hypochlorite.     How  would  you  write  the  symbol 
on  this  theory  ? 

21.  Represent  by  graphic  symbols  CaCO&  CaOv  CaOCl2. 

22.  The  percentage  composition  of  gypsum  is  calcium,  23.26  ;  sul- 
phur, 18.61 ;  oxygen,  37.21 ;  water,  20.92.     Calculate  the  symbol. 

23.  Is  the  incrustation  of  steam-boilers  by  insoluble  calcic  sulphate 
due  to  the  same  cause  as  the  incrustation  of  salt-pans  by  gypsum? 
Explain  the  difference. 

.  24.  If  the  calcium  contained  in  one  cubic  decimetre  of  anhydrite 
could  be  replaced  by  Hv  what  would  be  the  volume  of  the  product 
formed  ? 

.  25.  If  a  concentrated  solution  of  sodic  sulphate  is  mixed  with  a 
.concentrated  solution  of  calcic  chloride,  the  whole  mass  becomes 
solid.  Write  the  reaction,  and  explain  what  becomes  of  the  water 
of  solution. 

Ans.  (Na2SOt  -f  CaCl,  -f  2//20)  =  2NaCl  -f  CaSO^ .  2H^O. 

26.  How  could  you  detect  the  presence  of  sulphuric  acid  and  lime 
in  a  solution  of  gypsum?     Write  the  reactions 

27.  Represent  the  constitution  of  apatite  by  a  graphic  symbol. 

28.  How  may  you  regard  apatite  as  derived  from  calcic  hydrate  ? 
What  important  part  does  fluorine  play  in  the  compound  ?     Does 
not  the  presence  of  such  a  univalent  element  in  this  compound  fur- 
,nish  an  argument  in  favor  of  the  diatomicity  of  calcium  ? 

29.  How  much  hydrochloric  acid,  Sp.  Gr.  1.1,  will  be  required  to 
dissolve  50  grammes  of  chalk,  and  how  many  litres  of  O©g  could  be 
thus  obtained  ? 

Ans.  179  grammes  of  acid  and  11.16  litres  of  C0y 

30.  By  what  single  reaction  could  you  change  a  solution  of  calcic 
nitrate  into  a  solution  of  nitre  ? 

31.  What  evidence  do  you  find  in  this  section  that  calcium  is 
bivalent  ? 

32.  Compare  the  molecular  volumes  of  the  native  carbonates  of 
strontium,  barium,  and  lead  with  those  of  Aragonite  and  Calcite.  ' 

33.  Write  the  reactions  by  which  strontic  and  baric  sulphates  may 
be  prepared  from  the  corresponding  nitrates  or  chlorides. 

34.  Analyze  the  reactions  by  which  the  chlorides  and  nitrates  of 


352  EEACTIONS  AND  PROBLEMS. 

etrontium  and  barium  may  be  prepared  from  the  corresponding  sul- 
phates, and  show  why  such  a  circuitous  method  is  necessary. 

35.  Compare  the  molecular  volume  of  the  sulphates  of  this  group 
with  that  of  the  corresponding  carbonates. 

36.  How  may  solutions  of  calcic  and  strontic  sulphates  be  used 
to  detect  barium  and  strontium,  even  if  mixed  together  in  the  same 
solution  ? 

37.  Knowing  that  sulphuric  acid  if  in  excess  will  completely  pre- 
cipitate barium  and  strontium,  how  can  you  detect  the  presence  of 
lime  in  a  solution  containing  all  three  ? 

38.  On  what  does  the  use  of  the  salts  of  barium  as  tests  for  sul- 
phuric acid  depend  ? 

39.  To  how  much  S03  do  0.932  grammes  of  baric  sulphate  cor- 
respond ?  Ans.  0.320  grammes. 

40.  A  quantity  of  Witherite  weighing  0.591  grammes  was  dissolved 
in  hydrochloric  acid  and  precipitated  with  sulphuric  acid.     The  pre- 
cipitate when  washed,  dried,  and  ignited  weighed  0.699  grammes. 
What  per  cent  of  barium  does  the  mineral  contain  ? 

Ans.  69.37  per  cent. 

41.  Baric  and  strontic  carbonates  are  not,  like  calcic  carbonates, 
easily  decomposed  when  heated  in  the  air,  but  readily  give  off  COZ 
if  heated  in  an  atmosphere  of  hydrogen.     How  do  you  explain  these 
facts  ?  and  do  they  confirm  or  otherwise  your  answer  to  question  13  ? 

42.  What  is  the  percentage  of  lead  in  the  three  minerals  Angle- 
site,  Cerusite,and  Galena?  Ans.  68.32,  77.54,  86.62. 

43.  Analyze  reactions  [318  -  320]  and  state  the  general  theory  of 
the  smelting  process,  including  the  removal  of  the  gangue  and  the 
reduction  of  the  ore. 

44.  Explain  the  peculiar  action  of  lead  with  acid  solvents.    Why 
must  the  nitric  acid  be  diluted,  and  to  what  extent  ? 

45.  How  many  kilos,  of  litharge  can  be  obtained  from  37.1  kilos, 
of  lead,  and  what  volume  of  oxygen  gas  would  be  absorbed  in  the 
process?  Ans.  39.96  kilos,  and  2  in.8 

46.  Represent  the  plumbic  oxides  and  hydrates  by  graphic  sym- 
bols, and  show  how  the  basic  hydrates  are  related  to  the  assumed 
normal  hydrate. 

47.  The  action  of  nitric  acid  on  lead  depends  on  the  degree  of 
concentration  and  on  the  temperature.     Write  the  reaction  assuming 
that  NZ0  is  formed. 

48.  How  many  kilos,  of  crystallized  sugar  of  lead  can  be  made 
from  6.69  kilos,  of  litharge?  Ans.  11.37  kilos. 


REACTIONS  AND  PKOBLEMS.  353 

49.  How  much  litharge  will  a  solution  containing  11.37  kilos,  of 
sugar  of  lead  dissolve,  assuming  that  triplumbic  acetate  is  the  product 
formed  ?  Ans.  13.17  kilos.  PbO. 

50.  Write  the  reaction  of  COZ  on  a  solution  of  basic  acetate  of 
lead. 

51.  How  may  the  basic  acetates  be  regarded  as  derived  from  the 
normal  hydrates  ? 

52.  Write  the  reaction  of  dilute  sulphuric  acid  on  a  solution  of 
plumbic  nitrate. 

53.  Represent  the  constitution  of  pyromorphite  and  mimetene  by 
graphic  symbols. 

54.  What  is  the  derivation  of  the  name  pyromorphite  ? 

55.  Will  the  whole  of  the  lead  be  precipitated  from  its  solution  in 
acetic  acid  by  an  excess  of  HCl  -j-  Aqf 

56.  By  what  reagent  may  you  precipitate  the  whole  of  the  lead 
from  a  solution  of  one  of  its  salts  ? 

57.  Why  should  a  solution  of  PbO  in  lime-water  blacken  the  hair 
or  any  other  organic  material  containing  sulphur  ? 

58.  How  could  you  detect  the  presence  of  lead  in  water  ? 

59.  From  a  solution  containing  all  the  members  of  this  group,  how 
could  you  separate  the  whole  of  the  lead  ? 

60.  The  solubility  of  the  corn-pounds  of  the  elements  of  this  group 
diminishes,  as  a  general  rule,  in  proportion  as  the  atomic  weight  of 
the  metallic  radical  increases.     Does  this  fact  conform  to  the  law 
which  generally  obtains  in  chemical  series  in  regard  to  the  chemical 
energy  of  the  different  members  ? 


354  MAGNESIUM,  [§308. 


Divisions  VI.  and  VII. 

308.  MAGNESIUM.  Mg  =  24  —  Dyad,      One   of  the 
most  widely  distributed  elements,  although  not  so  abundant  as 
Calcium,  with  which  it  is  usually  associated*     In  some  of  its 
relations  it  is  very  closely  allied  to  calcium,,  but  also  differs 
from  it  in  many  important  respects. 

309.  Metallic  Magnesium,  Mg,  is  readily  obtained  by  decom- 
posing the  anhydrous  chloride  with  metallic  sodium,  also  by 
electrolysis.     It  is  a  silver-white  metal,  melting  at  a  red  heat, 
and  volatilizing  at  a  high  temperature  in  an  atmosphere  of  hy- 
drogen.    It  is  malleable  and  ductile,  is  susceptible  of  a  high 
polish,  and  does  not  tarnish  in  dry  air.     Heated  in  the  air  it 
takes  fire  and  burns  with  great  splendor  [59J,  and  it  is  now 
much  used  as  a  source  of  pure  white  light  when  great  bril- 
liancy is  required.     Boiling  water  acts  upon  the  metal  quite 
rapidly,  but  it  decomposes  cold  water  only  very  slowly. 

310.  Magnetic  Oxide  (Calcined  Magnesia) ,  MgO,  is  obtained 
when  the  metal  is  burnt  in  air.     It  can  also  be  obtained  by  cal- 
cining the  carbonate  or  the  nitrate.     It  is  a  bulky  white  powder, 
wholly  infusible,  and  emitting  a  bright  white  light  when  heated 
before  the  blow-pipe.     Intensely  heated,  it  appears  to  volatilize 
unchanged.     When  mixed  with  water  it  slowly  unites  with  it 
to  form  a  hydrate.     The  oxide  obtained  by  calcining  the  nitrate 
is  much  denser  than  that  made  from  the  carbonate,  and  possesses 
remarkable  hydraulic  qualities.     When  mixed   with  water,  it 
soon  sets  forming  a  hard  compact  mass  resembling  marble.     If 
the  oxide  is  heated  to  a  very  high  temperature,  it  loses  its  power 
of  uniting  with  water,  and  dissolves  only  slowly  even  in  the  strong- 
est acids.     Crystallized  MgO  (Figs.  5  to  7),  Periclase,  has  been 
found  in  small  grains  imbedded  in  a  limestone  rock  ejected  from 
Vesuvius,  but  otherwise  it  does  not  occur  uncombined  in  nature. 

311.  Magnetic  Hydrate,  Mg=OfH^  is  found  native,  crystal- 
lized in  large  hexagonal  plates  (76),  Brucite.     It  can  be  read- 
ily formed  artificially  as  above,  also  by  adding  caustic  potassa, 
soda,  or  baryta  to  the  solution  of  any  of  its  salts.     It  is  but 
very  slightly  soluble  in  water,  yet  sufficiently  to  give  a  distinct 
alkaline  reaction  (39).     It  absorbs  O02  slowly  from  the  air,  but 
much  more  slowly  than  calcic  hydrate. 


§313.]  MAGNESIUM.  355 

312.  Magnetic  Carbonate.    Mg=02=CO.     Sp.  Gr.  3.056.— 
The  mineral  Magnesite,  isomorphous  with  Calcite.     Insoluble 
in  pure  water,  but  in  carbonic  acid  water  more  soluble  than 
calcic  carbonate.     This  solution  is  much  used  as  a  medicine 
(liquid  magnesia).     If  exposed  to  the  air,  the  magnesic  car- 
bonate slowly  separates  in  crystalline  flakes,  containing  three 
atoms  of  water.     Anhydrous  magnesic  carbonate  is  not  readily 
obtained  artificially.     The  precipitate  obtained  on  adding  to  a 
boiling  solution  of  a  magnesia  salt  sodic  carbonate  is  a  mixture 
of  magnesic  carbonate  and  magnesic  hydrate  in  variable  pro- 
portions (Magnesia  Alba).     The  product,  however,  appears  to 
be  rather  a  mixture  of  several  definite  compounds  of  these  two 
salts ;  and  a  crystalline  mineral  is  known  called  Hydromagnesite, 
which  has  the  formula  H^Mgf>l2G^ .  2ff20  or 

Hof(C*MgofC*MgofC)  .  2ff20. 

Magnesic  carbonate  is  found  united  with  calcic  carbonate  in 
the  mineral  Dolomite  (Sp.  Gr.  2.9).  This  is  by  far  the  most 
abundant  native  compound  of  magnesium,  and  forms  in  many 
localities  extensive  beds  of  rocks.  It  occurs  in  large  and  well- 
defined  crystals  which  are  isomorphous  with  calcite  and  magne- 
site  (Fig,  16).  The  mineral  is  somewhat  variable  in  its  com- 
position, and  may  either  be  regarded  as  an  isomorphous  mixture 
of  these  two  substances,  or  else  as  a  definite  compound  mixed 
with  an  excess  of  one  or  the  other  of  its  constituents. 

MaC03+CaC03     or      Mgo-(G-02=G)-Cao. 

When  calcined  at  not  too  high  a  temperature,  the  magnesic  car- 
bonate is  alone  decomposed,  and  a  product  obtained  which  forms 
an  excellent  hydraulic  cement.  From  the  calcined  mass  the 
magnesia  can  be  dissolved  out  by  carbonic  acid  water  and  freed 
from  the  lime.  In  this  way  pure  magnesic  carbonate  is  pre- 
pared. 

313.  Magnesic  Sulphate  (Epsom  Salt).    MaS04  .  7ff20.  — 
The  most  important  soluble  salt  of  magnesia.     Obtained  from 
the  bittern  of  sea-water,  or  by  treating  the  native  carbonates  or 
Dolomite  with  sulphuric  acid.     It  is  a  very  common  ingredient 
of  mineral  waters,  like  those  of  Epsom,  and  is  formed  when 
water  saturated  with  gypsum  filters  through  Dolomitic  rocks. 


356  MAGNESIUM.  [§314. 

The  salt,  with  seven  molecules  of  water,  is  dimorphous,  crystal- 
lizing both  in  orthorhombic  forms  isomorphous  with  ZnS04  . 
7HO,  and  in  monoclinic  forms  isomorphous  with  FeSO^  .  1  HO. 
It  may  also  be  obtained  crystallized  with  1,  2,  3,  ....  12  mole- 
cules of  water  under  regulated  conditions,  chiefly  of  temperature. 
The  compound  MgS04  .  JT20  (Kieserite)  is  found  in  the  Stass- 
furt  salt-beds.  Epsom  salt  is  reduced  to  the  same  composition 
when  heated  to  150°,  but  the  last  molecule  of  water  is  retained 
even  at  200°,  and  this  leads  us  to  believe  that  it  forms  a  part 
of  the  molecule  of  the  salt,  whose  formula  would  then  be  writ- 
ten, Mgo=SO=Hop  This  opinion  is  confirmed  by  finding  that 
this  molecule  of  water  may  be  replaced  by  the  molecule  of  an 
alkaline  sulphate,  forming  a  double  salt,  which  crystallizes  with 
6ff20  in  tKe  same  form  as  magnesic  sulphate  with  7H20.  The 
symbol  of  the  potash  salt  is 

Mgo=(SO=02=OS)=Ko2. 


Epsom  salt  dissolves  in  about  three  times  its  weight  of  cold 
water.  It  is  a  valuable  medicine,  but,  like  all  the  soluble  salts 
of  magnesium,  it  has  a  bitter,  disgusting  taste. 

314.  Magnesic  Silicates.  —  The  well-known  minerals,  Ser- 
pentine, Talc  (Soap-Stone),  and  Chrysolite  (Olivine),  are  es- 
sentially magnesic  silicates  ;  and  in  many  other  native  silicates, 
including  the  Hornblendes,  Augites,  Chlorites,  and  some  vari- 
eties of  Mica,  magnesium  is  one  of  the  principal  basic  radicals. 

315.  Magnesic  Chloride.   MgOl2.  —  Found  dissolved  in  sea- 
water,  and  the  cause  of  its  bitter  taste.     Obtained  by  dissolving 
magnesic  carbonate  in  hydrochloric  acid,  and  evaporating  in  an 
atmosphere  of  hydrochloric  acid  gas.      If  evaporated  in  the  air, 
the  salt  is  partially  decomposed.    Very  fusible.    Used  for  making 
magnesium.      Forms  double  salts  with  alkaline  chlorides  (134). 

316.  Characteristic    ^Reactions.  —  Magnesium,     although 
closely  related  to  calcium,  is  distinguished  from  the  alkaline 
earths  by  the  great  solubility  of  its  sulphate,  also  by  its  ten- 
dency to  form  soluble  double  salts  with  ammonium,  in  conse- 
quence of  which  no  precipitate  is  formed  in  solutions  of  its  salts 
either  by  ammonia  or  ammonic  carbonate,  when  sufficient  excess 
of  some  ammonia  salt  is  present.     The  ammonic  magnesian 
phosphate,  however,  (NH^)2,Mg^O&lP202  .  l2ff2O  is  insoluble, 
and  is  formed  whenever  sodic  phosphate  is  added  to  an  am- 
moniacal  solution  of  a  magnesium  salt.     This  reaction  furnishes 
the  most  delicate  test  for  magnesium  salts. 


§320.]  ZINC.  357 

317.  ZINC.  Zn  ==  65.2.  —  Dyad.     One  of  the  more  abun- 
dant metallic  elements.     The  principal  ores  are 

Red  oxide  of  Zinc1  ZnO  Hexagonal, 

Blende  ZnS  Isometric, 

Smithsonite  Zno  =  CO  Hexagonal, 

Calamine  Zno^Si .  2H2  0  Trimetric. 

The  ores  are  reduced  by  first  roasting  or  calcining  until  the 
metal  is  in  the  condition  of  an  oxide,  and  then  distilling  with 
a  mixture  of  coal  in  earthen  retorts  or  muffles. 

318.  Metallic  Zinc.   Zn.  —  Sp.  Gr.   6.8  to  7.2.      Fuses  at 
500°.     Boils  at  a  red  heat.     The  polished  surface  has  a  bright 
lustre,  with  a  bluish  tint,  but  soon  tarnishes  in  moist  air.    Has 
a  crystalline  structure,  but,  although  brittle  both  at  a  high  and 
a  low  temperature,  it  may  readily  be  rolled  out  into  sheets  at  a 
temperature  of  about  140°.     Sheet-zinc  is  nearly  as  cheap  as 
sheet-iron  ;  and  since  it  does  not  rust,  or  at  most  only  very  su- 
perficially, it  is  preferable  for  many  purposes.     Iron,  however, 
is  a  much  stronger  metal,  and  is  frequently  coated  with  zinc  to 
protect  it  from  rusting.     It  is  then  said  to  be  galvanized.     Zinc 
readily  dissolves  in  dilute  acids  with  the  evolution  of  hydrogen, 
and  is  much  used  in  the  laboratory,  together  with  dilute  sul- 
phuric acid,  for  making  this  gas.     The  metal  is  first  granulated 
by  pouring  it,  when  melted,  into  water.     When  boiled  with  a 
solution  of  caustic  soda  or  potash,  it  also  dissolves  with  evolution 
of  hydrogen. 

Zn  +  (2Ko-ff+  Aq)  =  (KofZn  -f  Aq)  +  SHS.   [330] 

It  is  used  as  the  electro-positive  metal  in  the  galvanic  battery. 

319.  Zincic  Oxide,  ZnO,  which  is  made  in  large  quantities 
by  burning  zinc  vapor  at  the  mouth  of  the  reduction  furnaces, 
is  a  very  light  white  powder,  much  used,  when  mixed  with  oil, 
as  a  white  paint.     A  denser  oxide  is  obtained  by  calcining 
zincic  nitrate. 

320.  Zincic  Hydrate,  Zn=Ho^  is  formed  by  the  reaction 

(ZnSO,  +  ^K-Ho  +  Aq)  =  Zn-Ho2  +  (K^SO^-\- Aq),  [331] 
but  is  soluble  in  an  excess  of  reagent. 

1  The  color  is  due  to  the  presence  of  a  small  amount  of  manganese. 


358  ZINC.  [§321. 

321.  Zincic  Carbonate,  ZnC03,  is  isomorphous  with  magne- 
site  and  calcite.    When  prepared  by  precipitation,  a  mixture  of 
hydrate  and  carbonate  is  formed,  as  in  (312). 

322.  Zincic  Sulphate  (White  Vitriol).  ZnS04.7ff20.—Very 
soluble  salt,  isomorphous  with  Epsom  salt,  which  it  closely  re- 
sembles in  most  of  its  chemical  relations,  forming  similar  double 
salts.     Preparation  as  in  [64].     Used  in  pharmacy. 

323.  Zincic  Chloride.  ZnCl2.  —  A  solution  of  zinc  in  hydro- 
chloric acid  can  be  concentrated  by  evaporation  without  decom- 
position.    All  the  water  is  not  driven  off  until  the  temperature 
reaches  250°.     The  result  is  a  thick  syrup,  which  forms,  on 
cooling,  a  white,  deliquescent  solid,  melting  at  100°,  called  by 
the  alchemists  Butter  of  Zinc.     It  has  an  intense  affinity  for 
water,  and  by  its  aid  the  elements  of  water  may  frequently  be 
removed  from  a  chemical  compound  without  producing  any 
further  change.     Thus,  alcohol  may  be  converted  by  it  into 
ether  or  ethelyne.     According  to  the  proportions  used,  we  have 


or   2C2HQ0—IT20  =  2C2ff50.  [332] 

Ethylene.  Ether. 

For  the  same  reason  it  acts  as  a  cautery  on  the  skin.  It  is 
also  used  in  solution  as  an  antiseptic  and  disinfecting  agent. 

324.  Zinc  and  the  Alcohol  Eadicals.  —  Zinc  Methide, 
Zn=(Cffs)2;  ZmcEthide,£w=(Q^)2;  Zinc  Amylide,^=((75J7n)2. 
Observed  0p.  (S>r.  of  vapor,  3.29,  4.26,  and  6.95  respectively. 
Obtained  both  by  heating  zinc  with  the  iodides  of  methyl,  ethyl, 
or  amyl  in  sealed  tubes,  and  by  the  action  of  zinc  on  the  mer- 
cury compounds  of  the  same  radicals.  They  are  all  three 
colorless,  transparent,  strongly  refracting,  and  mobile  liquids. 
They  are  also  volatile,  boiling  at  the  temperatures  of  46°,  118°, 
and  220°  respectively.  They  are,  likewise,  highly  inflammable, 
and  the  first  two  take  fire  spontaneously  in  the  air.  As  these 
compounds  do  not,  as  a  whole,  combine  with  any  of  the  ele- 
ments, their  molecules  are  evidently  saturated,  and  they  are 
interesting  as  fixing  beyond  all  doubt  the  atomic  relations  of 
zinc.  Moreover,  they  are  useful  reagents  in  many  processes 
of  organic  chemistry. 

325.  Characteristic  Reactions.  —  •  Zinc,  like  magnesium, 
forms  soluble  double  salts  with  ammonia,  but  it  is  easily  distin- 
guished by  the  fact  that  its  sulphide  is  insoluble,  not  only  in 


§326.]  INDIUM.  —  CADMIUM.  359 

solutions  of  the  fixed  alkalies,  but  also  in  those  of  ammonia  and 
its  salts.  Hence  it  is  precipitated  from  all  alkaline  solutions  by 
sulphuretted  hydrogen.  The  sulphide  thus  obtained  is  a  white 
precipitate,  soluble  in  dilute  mineral  acids,  but  insoluble  in 
acetic  acid. 

326.  INDIUM.  In  =  72.  Sp.  Gr.  7.42.  CADMIUM. 
Od=  112.  Sp.  Gr.  8.69.  — Dyads.  Two  rare  metallic  ele- 
ments associated  with  zinc.  Indium  only  in  exceedingly  mi- 
nute quantities,  and  at  very  few  localities.  Cadmium  far  more 
generally,  and -in  much  larger  amounts.  Indium  is  less  vola- 
tile, and  cadmium  more  volatile,  than  zinc,  and  hence  in  distill- 
ing zinc  from  its  ores  the  cadmium  is  found  in  the  "  zinc  dust" 
which  is  collected  in  the  early  stage  of  the  process,  while  the 
indium  comes  over  later  with  the  great  mass  of  the  zinc,  with 
which  it  remains  alloyed.  With  sufficient  differences  to  mark 
their  individuality,  these  metals  resemble  zinc  in  almost  every 
particular.  They  form  similar  oxides  and  hydrates,  similar  sol- 
uble salts  with  hydrochloric,  nitric,  and  sulphuric  acids,  similar 
soluble  compounds  with  ammonia  salts,  similar  light-colored  sul- 
phides insoluble  in  alkaline  solutions  and  acetic  acid.  Cadmi- 
um differs  from  the  others  in  this  respect,  that  its  hydrate  is 
insoluble  in  caustic  soda  or  potash,  its  basic  carbonate  insoluble 
in  excess  of  ammonic  carbonate,  and  its  yellow  sulphide  insolu- 
ble in  dilute  mineral  acids.  This  sulphide  is  found  in  nature, 
and  the  mineral  is  called  Greenockite.  Zinc  precipitates  cad- 
mium from  solutions  of  its  salts,  and  both  zinc  and  cadmium 
precipitate  indium.  Indium  and  cadmium  are  more  fusible  than 
zinc,  and  form  very  fusible  alloys.  Indium  melts  at  176°,  cad- 
mium at  242°,  and  an  alloy  of  cadmium  with  lead,  tin,  and  bis- 
muth has  been  made  which  melts  at  60°.  Cadmium  boils  at 
860°,  and  the  Sp.  Gr.  of  its  vapor  has  been  found  by  obser- 
vation to  be  56.85.  Indium  and  cadmium  burn  when  heated 
before  the  blow-pipe,  the  first  yielding  a  yellow,  and  the  last 
a  brown  oxide,  very  unlike  the  white  oxide  of  zinc.  Although 
go  closely  allied  to  magnesium  and  zinc,  these  associated  ele- 
ments probably  belong  to  a  different  although  parallel  series, 
and  the  relation  between  the  atomic  weights  of  the  four  ele- 
ments is  in  harmony  with  this  view.  All  these  four  metals 
show  very  characteristic  bands  with  the  spectroscope,  and  in- 
dium was  first  discovered  by  the  well-marked  indigo-blue  band, 
from  which  it  takes  its  name. 


360  QUESTIONS   AND   PROBLEMS. 

Questions  and  Problems. 

1.  Write  the  reaction  of  sodium  on  magnesic  chloride. 

2.  When  water  is  decomposed  by  magnesium,  what  are  the  prod- 
ucts ?     Write  the  reaction.     [43.] 

3.  How  do  you  account  for  the  intense  brilliancy  of  the  light 
emitted  by  burning  magnesium?     (95.) 

4.  Write  the  reaction  of  water  on  calcined  magnesia.     [45.] 

5.  Write  the  reaction  of  solution  of  caustic  soda  on  solution  of 
magnesic  chloride. 

Ans.  (MgClz  +  2NaHo  -f  Aq)  =  MgHo^  -f  (2NaCl  -J-  Aq.) 

6.  Represent  the  composition   of   hydromagnesite    by    graphic 
symbols. 

7.  Represent,  graphically,  the  compound  radicals  Mgo,  Cao,  Zno, 
and  show  their  relations  to  hydroxyl. 

8.  Represent)  graphically,  the  composition  of  Dolomite. 

t  9.   What  do  you  understand  by  the  term  isomorphous  mixture  ? 

10.  Explain  the  theory  of  the  preparation  of  magnesic  carbonate 
from  Dolomite. 

11.  The  symbol  of  magnesic  sulphate  may  be  written  MgSO±, 
or  Mg=Oz=SO^  or  Mgo=SOz.     What  different  ideas  do  these  forms 
suggest  V 

12.  Write  the  reaction  of  sulphuric  acid  on  the  two  constituents 
of  dolomite,  and  show  how  pure  Epsom  salt  may  be  thus  prepared. 

13.  Write  the  reaction  of  a  solution   of  gypsum  on  magnesic 
carbonate. 

14.  Represent  by  graphic  symbols  MgSO^ .  HZ0. 

15.  Represent  by  graphic  symbols  the  composition  of  potassic 
magnesic  sulphate,  and  explain  the  relations  of  the  crystallized  salt 
to  Epsom  salt. 

16.  Write  the  reaction  of  hydrochloric  acid  on  magnesic  carbonate. 

17.  Explain  the  decomposition  which  results  when  a  solution  of 
magnesic  chloride  is  evaporated  in  the  air,  and  why  an  atmosphere 
of  II  Cl  should  prevent  the  change. 

18.  What  is  the  difference  between  the  relations  of  baric  and 
magnesic  carbonate  to  calcic  carbonate  ? 

Ans.  The  first  is  related  to  Aragonite,  the  second  to  Calcite. 

19.  What  is  the  difference  between  the  reactions  of  sodic  carbon- 


QUESTIONS  AND  PROBLEMS.  361 

ate  on  solutions  of  calcic  and  magnesic  salts,  and  on  what  does  the 
difference  depend  ?     Write  the  reactions  in  the  two  cases. 

20.  What  is  the  difference  between  the  reaction  of  ammonic  car- 
bonate on  the  same  solutions  ? 

21.  Write  the  reaction  of  sodic  phosphate  on  a  solution  of  mag- 
nesic and  ammonic  chloride. 

Ans.  (MgCli  +  NH3  +  HJTofOfPO  +  Aq)  = 

(NHJ,MgK>3;PO  .  6H20  -f  (2NaCl  +  Aq.) 

22.  Write  the  reactions  when  zinc  blende  and  smithsonite  are 
calcined. 

Ans.   ZnC03  =  ZnO  -j-  CO,,  and  2ZnS  -f  3(o)=(o)  = 

2ZnO 


23.  Write  the  reaction  when  zincic  oxide  is  reduced. 

Ans.  ZiiO  +  C  =  Sn 

24.  Write  the  reactions  of  dilute  sulphuric,  hydrochloric,   and 
acetic  acids  on  zinc. 

25.  What  part  does  zinc  play  in  reaction  [330]  ? 

26.  In  what  different  ways  may  the  symbol  of  zincic  hydrate  be 
written?  Ans.   Zn=0=2H2,  Zn=Ho2,  Zno=H2. 

27.  When  zincic  hydrate  dissolves  in  caustic  soda,  what  is  formed  ? 

28.  Write  the  reaction  of  sodic  carbonate  upon  a  solution  of  zincic 
sulphate,  assuming  that  three  molecules  of  zincic  hydrate  are  formed 
to  every  two  molecules  of  zincic  carbonate. 

Ans.  (5ZnSO,  -f-  5Na,COs  -f  SH,0  +  Aq)  = 

2ZnC03  -f  3ZiiHo2  -f  (5Na2SO,  -f-  Aq)  +  3@©2. 

29.  In  what  different  ways  may  the  symbol  of  zincic  sulphate  be 
written,  both  the  anhydrous  salt  and  the  salt  with  one  molecule  of 
water  ?     Represent  graphically. 

30.  Write  the  symbol  of  potassic  zincic  sulphate.     What  is  the 
crystalline  form  of  this  double  salt,  and  with  how  many  molecules  of 
water  does  it  crystallize  ? 

31.  Write  the  reaction  of  ammonic  sulphide  on  a  solution  of  zincic 
sulphate. 

Ans.  (ZnSO,  +  (NH,\S  -f  Aq)  = 


32.  Write  the  reaction  of  sulphuretted  hydrogen  on  a  solution  of 
zincic  acetate. 

33.  Would  zincic  sulphide  be  precipitated  from  a  solution  of  zincic 
chloride  containing  an  excess  of  hydrochloric  acid  ?     What  is  the 
difference  between  this  case  and  that  of  32  ?     (21.) 

16 


362  QUESTIONS  AND  PROBLEMS. 

Cadmium. 

34.  Write  the  reaction  of  dilute  sulphuric  acid  on  cadmium. 

35.  Write  the  reaction  of  sodic  hydrate  on  solution  of  cadmic 
sulphate. 

36.  Write  the  reaction  of  zinc  on  solution  of  indium  chloride. 

37.  Write  the  reaction  of  sulphuretted  hydrogen  on  solution  of 
cadmic  chloride. 

38.'  By  what  reactions  may  cadmium  be  separated  from  zinc  ? 
Ans.  By  metallic  zinc,  by  aminonic  carbonate,  and  by  sulphuret- 
ted hydrogen. 

39.  What  is  the  electrical  order  of  magnesium,  zinc,  indium,  and 
cadmium  ? 

40.  Assuming  that  the  atomic  weight  of  cadmium  is  112,  what  in- 
ference may  be  drawn  from  the  Sp.  Gr.  of  its  vapor  in  regard  to  the 
constitution  of  its  molecule  ?     Does  the  conclusion  have  any  bearing 
on  the  other  dyad  elements  ? 


§  328.]  GLUCINUM.  —  YTTRIUM.  —  ERBIUM.  363 


Divisions  VIII.  and  IX. 

327.  GLUCINUM.    Gl  =  9.3.  —  Dyad.     A  metallic  ele- 
ment, found  only  in  the  Beryl,  Glozl(Si6Ob)lAl^  the  Chryso- 
beryl,  Glo=Al202,  and  a  few  other  rare  minerals.     The  metal  is 
very  light,  Sp.  Gr.  2.1,  is  malleable,  has  a  bright  white  lustre, 
does  not  alter  in  the  air  even  when  heated,  and  does  not  decom- 
pose aqueous  vapor  at  a  red  heat.     It  resembles  aluminum,  as 
do  also  its  oxide,  hydrate,  and  chloride  the  corresponding  com- 
pounds of  the  same  metal.     The  hydrate  differs,  however,  from 
that  of  aluminum  in  several  important  respects.     Although  sol- 
uble in  caustic  alkalies,  it  is  again  precipitated  on  boiling  the 
diluted  solution.     It  dissolves  in  solutions  of  carbonate  of  am- 
monia, with  which  it  forms  a  crystalline  salt.     It  yields  with 
sulphuric  acid  a  well-crystallized  sulphate,  GIS04 .  4/^0,  which 
forms  with  potassic  sulphate  a  double  salt,  K^GU(SO^)Z .  2^0, 
wholly  different  from  alum.     Lastly,  it  absorbs  O02  from  the 
air.     The  salts  of  this  metal  have  an  acid  reaction  and  a  sweet 
taste,  whence  the  name  from  y\v<vs. 

328.  YTTRIUM,   T=61.7,  and  ERBIUM,  ^—112.6. 
- —  Dyads.     Metallic  elements  associated  together  in  Gadolinite, 
Yttrotantalite,  and  a  few  other  very  rare  minerals.     First  rec- 
ognized in  the  specimens  from  Ytterby,  in  Sweden,  whence  the 
names.     In  most  of  their  relations  they  quite  closely  resemble 
glucinum.     They  differ,  however,  from  it  in  forming  insoluble 
oxalates,  and  hence  are  precipitated  on  adding  an  excess  of  ox- 
alic acid  to  solutions  of  their  salts.     Their  hydrates  also  are  in- 
soluble in  caustic  soda  or  potash,  although  they  dissolve  readily 
in  solutions  of  ammonia  and  its  carbonate.  The  oxide  of  yttrium 
is  white,  that  of  erbium  slightly  rose-colored.      Oxide  of  er- 
bium, when  heated  in  a  colorless  flame,  shines  with  a  green  light, 
although  it  does  not  volatilize ;  and  with  the  spectroscope  the 
unique  phenomenon  is  seen  of  brilliant  colored  bands  superim- 
posed on  a  continuous  spectrum.     Moreover,  solutions  of  erbium 
salts  absorb  the  same  colored  rays  which  the  ignited  oxide 
emits ;  and  when  a  luminous  flame  is  viewed  with  a  spectro- 
scope through  such  a  solution,  dark  bands  are  seen  which  have 
the  same  position  as  the  luminous  bands  just  mentioned.     The 
salts  of  yttrium  exhibit  no  phenomena  of  this  kind. 


364  QUESTIONS  AND  PROBLEMS.  [§329. 

329.  CERIUM.  <7e  =  92.  LANTHANUM.  Za  =  93.6. 
DIDYMIUM.  D  =  95.  —  These  three  rare  elements  are  found 
inseparably  united  in  Cerite,  Allanite,  Lanthanite,  Yttrocerite, 
Parisite,  and  several  other  very  rare  minerals.  They  are  not 
unfrequently  associated  with  the  elements  of  the  last  section, 
which  they  resemble  in  many  particulars,  but  they  differ  from 
them  in  forming  with  potassium  insoluble  double  sulphates,  and 
hence  they  are  precipitated  on  adding  an  excess  of  potassic  sul- 
phate to  solutions  of  their  salts.  They  all  yield  oxides  of  the 
form  RO,  but  cerium  differs  from  the  other  two  in  forming  a 
higher  oxide,  probably  Ce304,  which,  when  heated  with  hydro- 
chloric acid,  evolves  chlorine.  The  oxides  of  cerium  and  lan- 
thanum are  more  or  less  colored,  and  that  of  didymium  is  dark 
brown.  The  salts  of  didymium  are  pink  or  violet  colored,  and 
when  in  solution,  even  in  small  quantities,  absorb  powerfully 
certain  rays  of  light ;  and  the  spectrum  of  a  luminous  flame 
viewed  through  such  a  solution  shows  a  strong  absorption  band 
in  the  yellow  and  another  in  the  green.  As  these  bands  differ 
wholly  from  those  of  erbium,  they  enable  us  to  recognize  with 
certainty  the  presence  of  didymium,  as  none  of  its  associated 
elements  produce  any  such  effect.  Moreover,  since  the  char- 
acteristic absorption  bands  are  seen  with  reflected  as  well  as 
with  transmitted  light,  we  are  enabled  to  extend  this  mode  of 
investigation  even  to  opaque  solids. 

In  regard  to  the  elementary  substances  but  little  is  known. 
Cerium,  which  has  been  obtained  by  reducing  its  chloride  with 
sodium,  is  a  soft  metal  like  lead.  When  polished,  it  exhibits  a 
high  metallic  lustre,  and  its  specific  gravity  is  about  5.5. 

Questions  and  Problems. 

1.  Some  chemists  regard  glucina  as  a  sesquioxide,  like  alumina, 
and  hence  write  the  symbol  GIZO8.     What  would  then  be  the  atomic 
weight  of  glucinum  ?  Ans.   14. 

2.  By  what  two  reagents  may  the  elements  of  this  section  be  di- 
vided into  three  groups  V      Ans.  Oxalic  acid  and  potassic  sulphate. 

3.  When  mixed  with  the  other  allied  oxides,  the  amount  of  eerie 
oxide  present  may  be  determined  by  dissolving  out  of  contact  with 
the  air  a  weighed  amount  of  the  mixed  oxides  in  hydrochloric  acid, 
to  which  some  potassic  iodide  has  been  added,  and  then  finding  by 
[272]  the  quantity  of  iodine  thus  set  free.     Write  the  reactions  illus- 
trating the  theory  of  the  process. 

Ans.  in  part.  Ce&04  +  8HCI  =  3CeC?2  +  4H20  +CI-CL 


§330.]  NICKEL.  365 


Division  X. 

330.  NICKEL.  Ni  =  58.8.  —  Quantivalence  usually  two. 
One  of  the  less  abundant  metallic  elements.  The  chief  native 
compounds  are 


Breithauptite  Hexagonal 

Kupfernickel  Hexagonal 

Chloanthite  (Niccoliferous 

Smaltine)  Isometric 

Nickel  Glance         Isometric 
Rammelsbergite       Orthorhombic 
Millerite  Hexagonal       JWisS9 

Bunsenite  Isometric         Ni-O, 

Nickel  Vitriol          Monoclinic       Ni=02= 
Annabergite  (Nickel 

green)  Monoclinic       17i3EO£(AsO)2*  Sff20, 

Emerald  Nickel  (Zaratite)  Nis^06WO,ff4 .  ±ff.20, 

Genthite  \_Ni,Mg^  vui  08  vuiSis  02 .  Qff2  0. 


The  metal,  however,  is  obtained  chiefly  from  a  niccoliferous 
iron  pyrites  (magnetic  variety),  which  only  contains  the  element 
as  an  accessory  constituent.  The  native  arsenides,  and  an  im- 
pure regulus  (called  speiss)  formed  in  the  preparation  of  smalt, 
are  the  other  sources  of  the  nickel  of  commerce.  The  process 
of  extracting  the  metal  is  complicated  and  tedious.  It  consists 
in  roasting  the  ore,  dissolving  the  resulting  oxides  in  acid,  and 
precipitating  first  the  associated  metals,  and  afterwards  the 
nickel,  by  appropriate  reagents.  The  chief  difficulty  is  to  sep- 
arate from  the  nickel  the  more  valuable  cobalt,  with  which 
nickel  is  almost  invariably  associated,  and  to  which  it  is  very 
closely  allied. 

Metallic  nickel,  Sp.  Gr.  8.82,  has  a  silver-white  color,  a  bril- 
liant metallic  lustre,  and  does  not  tarnish  when  exposed  to  the 
atmosphere.  It  has  great  tenacity  and  malleability,  and,  were 
it  more  abundant,  would  rival  even  iron  in  the  number  of  its 
applications  in  the  useful  arts.  Nickel  resembles  iron  in  many 
of  its  qualities.  When  pure,  it  is  nearly  as  infusible  as  wrought- 


366  NICKEL.  [§330. 

iron,  and  may  be  forged  in  a  similar  way.  When  combined 
with  a  small  amount  of  carbon,  it  may,  like  cast-iron,  be  fused 
in  an  ordiwary  wind  furnace.  Nickel  is  also,  like  iron,  suscep- 
tible of  magnetism,  but  the  magnetic  power  is  less  marked,  and, 
when  heated,  it  loses  this  virtue  at  a  much  lower  temperature. 
Moreover,  like  iron,  nickel  is  soluble  in  dilute  sulphuric  or 
hydrochloric  acids  with  evolution  of  hydrogen  gas,  but  the  ac- 
tion is  less  energetic,  and  the  metal  dissolves  only  slowly.  The 
best  solvents  are  nitric  acid  and  aqua  regia.  Nickel  forms  with 
copper  a  brilliant  white,  hard,  tenacious,  malleable  alloy,  and 
a  small  amount  of  nickel  will  whiten  a  large  body  of  copper. 
This  alloy  is  much  used  for  coinage,  and  as  the  basis  of  the 
better  kinds  of  electrotype  plate.  German  silver  is  an  alloy  of 
copper,  zinc,  and  nickel  in  about  the  proportion  of  5:3:2. 
Nickel  may  also  be  alloyed  with  iron,  and  is  a  constant  constit- 
uent of  the  metallic  meteorites.  Nickel  readily  combines  with 
each  of  the  members  of  the  chlorine  group  of  elements,  but 
only  in  one  proportion,  and  the  compounds  thus  formed,  NiF& 
NiClz,  &c.,  are  all  soluble  in  water. 

There  are  two  oxides  of  nickel.  The  protoxide,  NiO,  is  an 
olive-green  powder,  readily  obtained  by  igniting  either  the  ni- 
trate or  the  carbonate  of  the  metal.  It  is  a  basic  anhydride, 
dissolving  readily  in  the  mineral  acids,  and  forming  the  ordinary 
nickel  salts,  in  all  of  which  Ni  acts  as  a  bivalent  radical.  The 
sesquioxide,  Ni203,  is  a  black  powder,  also  obtained  by  igniting 
the  nitrate,  but  at  a  lower  temperature.  It  is  an  unstable  com- 
pound, and,  when  heated,  is  resolved  into  the  lower  oxide  and 
oxygen  gas.  It  is  not  a  basic  anhydride,  and,  when  heated  wkh 
the  mineral  acids,  one  third  of  the  oxygen  is  given  off  as  before, 
and  a  salt  of  the  ordinary  type  is  the  result.  In  the  sesquiox- 
ide, Ni  is  a  quadrivalent,  but  the  double  atom  (Ni2)  acts  as  a 
sexivalent  radical.  The  tendency  to  form  radicals  of  this  last 
type,  which  is  only  foreshadowed  in  nickel,  becomes  a  striking 
character  in  the  elements  which  follow  in  our  classification. 

Of  the  crystallized  soluble  salts  of  nickel,  the  most  common 
are 

Niccolous  Chloride  Ni  C12 .  $ff2  0, 

Niccolous  Nitrate  Ni=02=(N02)2 .  6ff20, 

Niccolous  Sulphate  Ni,H^OfS 

Dipotassic-niccolous  Sulphate       Ni,Kf  Of(SOz)a . 


§331.]  COBALT.  367 

The  salts  of  nickel,  both  when  crystallized  and  when  in  so- 
lution, have  a  characteristic  green  color;  but,  when  rendered 
anhydrous  by  heat,  this  color  changes  to  yellow.  From  their 
solutions  the  fixed  alkalies  precipitate  a  hydrate,  arid  the  alka- 
line carbonates  a  basic  carbonate,  of  nickel,  both  forming  pale- 
green  precipitates.  The  first  is  probably  the  definite  compound 
Ni=OfHz',  but  the  composition  of  the  second  varies  with  the 
temperature,  strength,  and  proportions  of  the  solutions  em- 
ployed, and  the  product  is  closely  analogous  to  the  precipitates, 
which  are  obtained  under  similar  conditions  from  solutions  of 
the  salts  of  magnesium  or  zinc. 

The  salts  of  nickel  readily  combine  both  with  ammonia  and 
with  the  ammonium  salts.  A  large  number  of  products  may 
thus  be  formed,  which  are  easily  soluble  in  water.  The  fol- 
lowing crystalline  compounds,  which  indirectly  play  an  impor- 
tant part  in  some  of  the  methods  of  qualitative  analysis,  will 
serve  as  types  of  the  class :  — 

Ni  C12 .  6Nff3,  Nff4  Cl .  Ni  C12 .  6  #2  0. 

From  solutions  of  such  ammoniacal  compounds,  and  from 
other  alkaline  solutions  containing  nickel,  the  metal  is  precipi- 
tated as  [JV*2]i06LH!J,  both  by  chlorine  gas  and  by  the  alkaline 
hypochlorites.  The  precipitate  has  an  intense  black  color,  and 
this  reaction  is  one  of  the  most  delicate  tests  for  nickel,  but 
does  not  distinguish  it  from  cobalt.  Nickel  is  also  precipitated 
from  alkaline  solutions  by  Jf2S  or  by  alkaline  sulphides.  The 
black  precipitate  thus  obtained  has  the  same  composition  as 
Millerite,  NiS.  It  is  insoluble  in  the  dilute  mineral  acids,  al- 
though in  acid  solutions  of  nickel  salts  ff2S  gives  no  precipitate. 
Two  other  sulphides  of  the  element,  Ni2S  and  NiS2,  have  been 
described. 

331.  COBALT.  Co  =  58.8.  —  Quantivalence  usually  two. 
Associated  with  nickel  in  the  same  ores,  but  less  abundantly 
distributed.  Most  of  the  minerals  enumerated  in  the  last  sec- 
tion contain  cobalt.  When,  however,  this  metal  preponderates, 
they  are  in  most  cases  classed  as  separate  mineral  species,  and 
receive  distinct  names.  No  cobalt  mineral  corresponding  tc 
Kupfernickel  or  Breithauptite  has  been  found,  but  we  have 


368  COBALT.  [§331. 


Smaltine  Isometric 

Cobaltine  Isometric  Co^[S2,(As2)~\, 

Linnaeite  Isometric 

Glaucodot  Orthorhombic  Co 

Syepoorite  Co  ^/S, 

Cobalt  Vitriol  Monoclinic  Co=02=S02.7JT20, 

Erythrite  (  Cobalt  Bloom)  Monoclinic  Cb3!  OJ(  As  0)2  .  8H2  0. 

To  these  must  be  added  an  impure  oxide  of  cobalt  (Earthy 
Cobalt),  and  a  mineral  called  Remingtonite,  which  probably 
corresponds  to  Emerald  Nickel.  There  is  a  variety  of  Lin- 
nseite,  called  Siegenite,  which  contains  a  large  proportion  of 
nickel  ;  but  no  purely  niccoliferous  compound  of  this  type  is 
known. 

In  all  their  chemical  relations,  the  two  metals  here  associ- 
ated resemble  each  other  so  closely  that  the  description  of 
nickel  given  above  applies  almost  word  for  word  to  cobalt,  and 
it  is  only  necessary  to  indicate  farther  the  points  of  difference. 

Metallic  cobalt  rusts  more  readily  than  nickel,  but  less  read- 
ily than  iron.  It  is  magnetic,  and  possesses  valuable  qualities, 
but  is  so  costly  that  it  has  received  no  application  in  the  arts. 

Cobalt  forms  but  one  stable  compound  with  either  of  the  mem- 
bers of  the  chlorine  group  of  elements,  Co  C12,  &c.  ;  but  by  dis- 
solving Co208  in  hydrochloric  acid  a  red  solution  is  obtained, 
which  is  supposed  to  contain  Co2Cl6.  The  compound,  however, 
is  very  unstable,  for  the  solution  evolves  chlorine  on  the  slight- 
est elevation  of  temperature. 

There  are  three  well-marked  oxides  of  cobalt.  Cobaltous 
Oxide,  CoO-,  Cobaltic  Oxide,  Co203-,  Cobaltous-cobaltic  Ox- 
ide, Co304-,  but,  besides  these,  several  others  have  been  dis- 
tinguished, which  are  probably  either  mixtures  or  molecular 
aggregates  of  the  first  two.  Not  only  is  Co  0  a  strong  basic 
anhydride,  like  NiO,  but  also  Co208  dissolves  in  acids,  espe- 
cially in  acetic  acid,  forming  salts.  We  have,  therefore,  to  dis- 
tinguish between  cobaltous  and  cobaltic  salts  ;  but  the  last  are 
very  unstable  and  little  known. 

The  ordinary  cobaltous  salts,  when  crystallized,  are  red,  but 
are  usually  lilac-colored  when  anhydrous,  and  the  pink  solu- 
tions, which  they  yield  with  water,  become  blue  when  concen- 
trated. On  this  change  of  color  depends  the  virtue  of  certain 


§331.]  COBALT.  369 

sympathetic  inks.  From  solutions  of  these  salts,  potassic  or 
sodic  hydrate  precipitate  Co  =  02=ff2,  which  has  a  delicate  rose- 
color.  The  pale-blue  precipitate,  which  generally  falls  first,  is 
a  basic  salt  of  cobalt,  but  if  warmed  with  an  excess  of  the  re- 
agent, it  soon  acquires  the  composition  and  color  of  the  normal 
hydrate.  If  exposed  to  the  air  this  hydrate  absorbs  oxygen 
rapidly,  and  changes  to  a  dingy-green  color.  The  normal  co- 
baltic  hydrate  is  not  known.  The  black  precipitate  obtained 
by  the  action  of  chlorine  or  the  hypochlorites  on  alkaline  solu- 
tions containing  cobalt  is  the  second  anhydride  of  this  hydrate, 
or  0^\_  Co2]  =  Offfp  The  same  compound  is  formed  when  chlo- 
rine gas  is  passed  through  water  or  a  solution  of  caustic  potash 
holding  cobaltous  hydrate  in  suspension.  When  the  alkali  is 
used,  the  whole  of  the  hydrate  is  converted  into  the  cobaltic 
compound  ;  but  with  pure  water  only  two  thirds  as  much  are 
obtained.  The  compound  of  nickel  formed  under  the  same 
conditions  is  supposed  to  be  the  normal  niccolic  hydrate. 

The  tendency  to  form  soluble  compounds  with  ammonia  and 
with  the  ammonium  salts  manifested  by  nickel,  appears  again 
and  more  prominently  in  the  allied  element  cobalt.  Moreover, 
there  are  cobaltic  as  well  as  cobaltous  compounds  of  this  class, 
and  the  last  tend  to  pass  into  the  first  by  absorbing  oxygen 
when  exposed  to  the  air.  The  number  of  these  compounds  is 
very  numerous.  They  have  a  very  complex  constitution,  and 
in  many  cases  at  least  are  probably  formed  on  the  ammonia 
type.  We  may  regard  them  as  compounds  of  ammonio-cobalt 
bases,  to  several  of  which  distinctive  names  have  been  given. 
The  following  scheme  exhibits  the  relations  of  the  more  impor- 
tant compounds  :  — 

Cobaltous  Compounds. 
CoR  .  4Nff3,  CoR  . 


Cobaltic  Compounds. 

.    SNH3     Fusco-cobaltic  salts. 
n 

.  10JV/5     Roseo  or  Purpureo-cobaltic  salts. 

.  !2Nff3     Luteo-cobaltic  salts. 


ii 

In  the  above  symbols  R  stands  for  a  bivalent  acid  radical, 
16*  x 


70  COBALT.  [§331. 


like  (SOJ,  (C03),  (O204)  or  Cl»  (NO^  &c.  Substituting 
these  in  the  general  symbol,  we  obtain  the  specific  symbols  of 
the  various  salts  of  the  assumed  bases  j  but  in  most  cases  the 
crystallized  salt  contains  in  addition  one  or  more  molecules  of 
water,  which  frequently  play  an  important  part  in  its  constitu- 
tion, and  determine  marked  differences  of  qualities,  as  in  the 
following  typical  compounds  :  — 

Purpureo-cobaltic  Chloride     \_Co^\ClQ  .  WNH3, 
Roseo-cobaltic  Chloride  [<702]  C/6  .  WNff3  .  2ff20, 

Xantho-cobaltic  Chloride         [Co2]  C16  .  10NH3  .  N202 


Cobaltous  oxide  combines  with  many  of  the  basic  as  well  as 
with  the  acid  anhydrides,  yielding  in  several  cases  compounds 
distinguished  by  great  brilliancy  of  coloring.  The  compound 
with  [Al^Os  is  known  as  Thenard's  blue,  that  with  ZnO  as 
Rinman's  green.  Such  compounds  are  formed  when  the  me- 
tallic oxides,  moistened  with  a  solution  of  cobaltous  nitrate,  are 
heated  before  the  blow-pipe,  and  the  production  of  the  color  is 
one  of  the  most  characteristic  blow-pipe  reactions. 

Cobaltous  oxide,  when  melted  into  glass  or  into  the  glaze  of 
earthenware,  imparts  to  the  material  an  intense  blue  color,  and 
the  brilliancy  and  the  depth  of  the  color  render  the  oxide  one 
of  the  most  valuable  vitrifiable  pigments,  and  this  is  its  chief 
use  in  the  arts.  The  blue  pigment  called  smalt,  used  for  color- 
ing paper  and  dressing  white  calicoes^  is  a  pulverized  alkaline 
glass  strongly  colored  with  the  oxide. 

Cobalt  is  distinguished  by  the  same  reactions  as  nickel  from 
all  other  metallic  radicals.  From  nickel  it  is  distinguished,  — 
First,  by  the  blue  color  which  the  oxide  gives  to  borax  glass. 
Secondly,  by  the  fact  that  potassic  nitrite  precipitates1  the  co- 
balt from  nitric  or  acetic  acid  solutions,  while  it  does  not  precip- 
itate nickel.  Thirdly,  by  the  circumstance  that  cyanide  of  co- 
balt forms,  when  boiled  with  a  solution  of  potassic  cyanide  in 
contact  with  the  air,  a  compound  corresponding  to  potassic  ferri- 
cyanide.  The  solution  of  potassic  cobalti-cyanide  is  not  de- 
composed by  HgO  or  by  alkaline  hypochlorites,  while  from  the 
solution  of  the  cyanide  of  nickel  and  potassium,  formed  under 

1  Composition  of  precipitate  according  to  S.  P.  Sadtler, 
*e,  [Co2]xii012xii(2V202)8  . 


§331.]  QUESTIONS  AND  PROBLEMS.  371 

the  same  circumstances,  all  the  nickel  is  precipitated  by  the 
same  reagents. 

CoO+(2ff-CN+Ag)=Co°(CN)»+(B»0+Aq.)    [333] 

4Co=(CI¥)2  +  (12K-CN+  ±H-CN+  Aq)  +  (fiXe)  = 

(70,)  +  2IS0  +  Aq).  [334] 


WiO  +  (4JC-CN+  H20  +  Aq)  = 

(ZK-CN.  Ni-(  ON)2  +  2K-0-H+  Aq).  [335] 


HgO  +  (2K-CN.  Ni-(CN)2  + 

m=O2=H2  +  (ZK-CN.  ffff-(CN),  +  Aq).  [336] 


Questions  and  Problems. 

1.  Represent  by  graphic  symbols  the  constitution  of  Kupfernickel 
and  Chloanthite. 

2.  In  the  symbol  of  Nickel  Glance,  in  what  relation  does  the  sul- 
phur stand  to  the  arsenic  ?     Could  these  elements  replace  each  other 
by  single  atoms  ? 

3.  What  is  the  distinction  between  Chloanthite  and  Rammels- 
bergite  ?     Does  the  same  distinction  reappear  in  the  corresponding 
compound  of  either  of  the  allied  elements  ? 

4.  Have  any  facts  been  stated  which  prove  that  nickel  is  some- 
times quadrivalent  ? 

5.  Represent  by  a  graphic  symbol  the  constitution  of  niccolous 
sulphate. 

6.  Write  the  reaction  of  sulphuric  acid,  and  also  of  hydrochloric 
acid,  on 


7.  Point  out  the  analogies  between  nickel  and  zinc. 

8.  The  precipitate  first  formed  by  ammonia  or  ammonic  carbon- 
ate in  solutions  of  the  salts  of  nickel  redissolves  in  an  excess  of  the 
reagent,  and  does  not  form  at  all  when  a  large  amount  of  ammonic 
chloride  is  present.     How  do  you  explain  these  reactions  ? 

9.  In  the  native  compounds  of  cobalt  this  element  is  more  or  less 
replaced  by  iron  and  nickel.     Write  the  symbols  of  Smaltine  and 
Cobaltine  so  as  to  indicate  this  fact 


372  QUESTIONS  AND  PROBLEMS. 

10.  Represent  by  graphic  symbols  the  constitution  of  Linnaeite, 
and  also  that  of  Co2S3  and  CoS^  the  only  other  sulphides  not  men- 
tioned in  the  text. 

11.  Represent  by  graphic  symbols  the  constitution  of  the  follow- 
ing oxides  and  oxysulphides,  Co80v  Co60r  CozOS. 

12.  In  what  respects  do  the  oxides  and  sulphides  of  cobalt  differ 
from  those  of  nickel  ? 

13.  Write  the  reaction  of  chlorine  gas  on  cobaltous  hydrate,  first, 
when  suspended  in  water,  and,  secondly,  when  suspended  in  solution 
of  caustic  potash.      Write  also  the  corresponding  reactions  which 
take  place  when  hydrate  of  nickel  is  similarly  treated. 

14.  Represent  the  composition  of  the  ammonio-cobalt  salts  by 
typical  symbols. 

15.  In  potassic  cobalti-cyanide  what  is  the  quantivalence  of  co- 
balt ?     Do  the  cobalt  atoms  change  their  atomicity  in  [334]  ? 

16.  Analyze  reactions  [333]  to  [336],  and  show  that  the  differ- 
ences in  the  relations  of  cobalt  and  nickel  to  the  alkaline  cyanides 
depend  on   differences  in  the  atomic  relations  of  the  two  elements. 
What  part  does  the  oxygen  of  the  air  play  in  [334]  ? 

1 7.  Pojassic  cobalti-cyanide  is  formed  when  cobaltous  hydrate  is 
boiled  with  a  solution  of  potassic  cyanide,  there  being  free  access  of 
air.     Write  the  reaction. 

18.  Write  the  reaction  when  a  solution  of  potassic  hypochlorite 
(K-O-Cl}  is  added  to  the  product  of  reaction  [335]. 

19.  Point  out  the  resemblances  and  the  differences  in  the  chemi- 
cal relations  of  cobalt  and  nickel,  and  show  how  far  they  may  be 
traced  to  the  circumstance  that  the  radical  [Co2]  is  more  stable  than 
the  radical 


§  332.]  MANGANESE.  373 


Division  XL 

332.  MANGANESE.  Mn  =  55.  —  Quantivalence  two, 
four,  six,  and  possibly  eight.  A  tolerably  abundant  element, 
and  widely  diffused  throughout  the  mineral  kingdom,  entering 
into  the  composition  of  a  very  large  number  of  minerals.  The 
following  are  the  most  characteristic  or  important:  — 


Pyrolusite 

Orthorhombic 

Mn02, 

Braunite 

Tetragonal 

Mn203 

Hausmannite 

Tetragonal 

Mn304, 

Psilomelane 

Massive  ) 

Mixtui 

Wad 

Earthy   ) 

oxide 

Manganite 

Orthorhombic 

Of[M 

Hauerite 

Isometric 

MnS* 

Manganblende 

Isometric 

MnS, 

Rhodonite 

Triclinic 

Mn=02 

Tephroite 

Orthorhombic 

J.YLftxg2  ^-^4 

Triplite 

Orthorhombic 

Manganese  Spar    Rhombohedral       Mn=02=O01 
Mansano-calcite     Orthorhombic 


o1- 


The  elementary  substance  is  a  very  hard  and  brittle  metal,  Sp. 
Gr.  8.013.  It  has  a  grayish-  white  color,  is  almost  infusible, 
and  very  slightly  magnetic.  It  oxidizes  rapidly  in  moist  air, 
and  decomposes  water  even  at  the  ordinary  temperature. 
There  appear  to  be  two  conditions  of  the  metal  corresponding 
to  wrought  and  cast  iron  ;  but  its  properties  have  not  been 
thoroughly  studied.  It  is  obtained  with  difficulty  by  reducing 
the  oxide  with  carbon  at  a  very  high  temperature,  and  as  yet 
has  found  no  applications  in  the  arts.  Corresponding  to  the 
three  degrees  of  quanti  valence  of  Manganese  are  three  classes 
of  compounds. 

1.  Manganous  compounds,  in  which  the  quantivalence  of  the 
element  is  two.  This  class  includes  all  the  manganese  minerals 
above  enumerated,  after  manganblende,  and  all  the  common 
soluble  salts  of  the  metal.  Among  the  last  the  most  important 
are 


374  MANGANESE.  [§332. 


Manganous  Chloride  Mn  C12  .  (2  or 

Manganous  Sulphate  Mn=02=S02  .  (4,  5,  or  7ff2O), 

Dipotassic-manganous  Sulphate    K2,Mn^Of\_S02]2  .  §ff20. 


There  is  also  a  Bromide,  MnBrz  .  2ff20.  The  manganous 
compounds  are  distinguished  by  a  delicate  pink  or  red  color, 
From  solutions  of  the  manganous  salts,  potassic  or  sodic  hy- 
drate precipitate  a  white  hydrate,  Mn^O^H^  which  absorbs 
oxygen  rapidly,  and  becomes  brown  when  exposed  to  the  air 
(Manganese  Brown).  In  like  manner  sodic  or  potassic  car- 
bonate precipitate  a  white  hydro-carbonate,  which  also  becomes 
brown  on  drying.  Ammonic  carbonate  also  produces  the  same 
precipitate,  and  does  not  redissolve  it  when  added  in  excess. 
Ammonic  hydrate,  on  the  other  hand,  gives  no  precipitate  in 
solutions  containing  an  excess  of  ammonic  chloride,  and  redis- 
solves  the  precipitate  which  first  forms  in  simple  aqueous  solu- 
tions. Ammonio-manganous  salts  are  thus  formed,  and  two 
well-crystallized  ammonio-manganous  chlorides  have  been  de- 
scribed, MnCl2  .  2Nff4Ol  .  H20  and  MnCl2  .  NH4Cl  .  2ff20. 

In  the  solution  of  a  manganous  salt,  sodic  phosphate  and  am- 
monia produce,  under  regulated  conditions,  a  highly  crystalline 
precipitate  having  the  composition  (NH^)^Mn2lO^(PO)z  . 
2ff20.  This  precipitate  yields  on  ignition  a  pyrophosphate  of 
uniform  composition,  and  on  this  reaction  is  based  a  valuable 
means  of  determining  the  amount  of  manganese  in  quantitative 
chemical  analysis. 

Manganous  oxide,  Mn  0,  is  easily  obtained  by  reducing  either 
of  the  higher  oxides  with  hydrogen.  It  is  an  olive-green  pow- 
der, which  burns  if  heated  in  the  air,  thus  forming  the  "  red 
oxide"  Mn304. 

Manganous  sulphide  is  precipitated  on  adding  an  alkaline 
sulphide  to  the  solution  of  a  manganous  salt,  as  a  flesh-col- 
ored hydrate,  MnS  .  xH20  ;  but  this  also  in  contact  with  the 
air  rapidly  oxidizes  and  turns  brown.  It  readily  dissolves  in 
the  dilute  mineral  acids,  and  also  in  acetic  acid.  The  same 
tendency  to  form  compounds,  in  which  manganese  presents  a 
higher  order  of  quantivalence,  is  exhibited  by  all  the  soluble 
manganous  salts,  and  especially  by  the  ammoniacal  solutions  just 
mentioned,  which,  when  exposed  to  the  air,  rapidly  absorb  oxy- 
gen, become  turbid,  and  deposit  a  brownish  flocculent  precipitate 


§  332.]  MANGANESE.  375 


of  manganic  hydrate  (Of\_Mn^HfO^).  So,  also,  when  chlo- 
rine gas  is  passed  through  water  holding  manganous  hydrate  or 
carbonate  in  suspension,  or  through  a  solution  of  a  manganous 
salt,  to  which  an  excess  of  sodic  acetate  has  been  added,  the 
manganese  is  still  further  oxidized,  and  the  brownish  precipitate 
obtained  is  chiefly  a  hydrate  of  the  dioxide  Mn  02  .  H%0.  Bro- 
mine also  produces  a  similar  result. 

2.  Manganic  compounds,  in  which  the  quantivalence  of  the 
element  is  four.  Of  these  we  must  distinguish  two  divisions  : 
first,  those  which  have  for  their  radical  the  single  quadrivalent 
atom  of  manganese  ;  second,  those  in  which  two  such  quadriva- 
lent atoms  act  as  a  compound  radical  with  a  quantivalence  of 
six.  To  the  first  division  of  the  manganic  compounds  probably 
belong  most  of  the  native  oxides.  Pyrolusite,  Mn02,  has  a 
crystalline  form  similar  to  that  of  Brookite,  TiO*  which  is 
an  oxide  of  the  well-marked  tetrad  element  titanium  ;  while 
Braunite,  Mn203,  and  Hausmannite,  Mn304,  have  a  form  which 
is  nearly  isomorphous  with  Rutile,  an  allotropic  state  of  the 
same  oxide  (Fig.  37),  but  wholly  unlike  the  forms  of  J?e203 
(Fig.  44)  and  Fes04  (Fig.  33),  two  typical  compounds,  to 
which  Braunite  and  Hausmannite,  if  containing  the  sexivalent 
radical  [^Tw2],  must  be  closely  allied.  Manganite  probably 
contains  this  radical,  as  it  is  isomorphous  with  the  native  ferric 
hydrate,  Gothite. 

Of  the  oxides  of  manganese,  the  red  oxide,  Mns04,  is  the 
most  stable.  The  higher  oxides,  when  heated,  are  all  resolved 
into  Mn304,  and  the  native  oxides  thus  become  sources  of  oxy- 
gen gas  [232].  When  heated  with  sulphuric  acid,  they  also 
give  off  oxygen  and  yield  manganous  sulphate  [231].  When 
heated  with  hydrochloric  acid,  they  liberate  chlorine  and  yield 
manganous  chloride  [77].  Hence  an  important  application  of 
the  native  oxides  in  the  arts.  There  are  reasons  for  believing 
that  the  two  atoms  of  oxygen  in  Mn  02  stand  in  different  rela- 
tions to  this  molecular  group  (236),  and  the  chloride  of  man- 
ganese, MnCl±,  recently  isolated,  affords  still  more  conclusive 
evidence  of  the  quadrivalent  relations  of  this  element.  This 
manganic  chloride  is  exceedingly  unsta'ble,  and  when  gently 
heated  breaks  up  into  manganous  chloride  and  chlorine  gas. 

To  the  second  division  of  the  manganic  compounds  belong 
manganic  hydrate,  0£\_Mnz~\  =  OfH2,  and  several  very  unstable 


376  MANGANESE.  [§332. 

compounds,  which  have  been  formed  by  dissolving  this  hydrate 
in  different  acids.  The  sulphate,  however,  becomes  stable  when 
the  hexad  radical  is  associated  in  the  salt  with  potassium.  We 
thus  obtain  an  interesting  variety  of  alum, 


3.  The  most  characteristic  compounds  of  manganese  are 
those  in  which  the  element  is  either  sexivalent  or  octivalent, 
and  the  fact  that  a  volatile  fluoride  of  manganese  is  known, 
which  contains  at  least  six  atoms  of  fluorine  to  every  atom  of 
manganese,  indicates  that  the  atomicity  of  the  elements  cannot 
be  less  than  six.  Indeed,  the  fluorides  illustrate  very  strikingly 
the  different  degrees  of  quantivalence  which  manganese  may 
assume,  for  we  have  MnF2,  MnF±,  [Mn^\F&  and  MnF6. 

When  an  intimate  mixture  ofK-0-Ifa,i\dMti02  is  roasted  in 
a  current  of  oxygen  gas,  the  following  reaction  takes  place:  — 


4K-0-H  +  2]fln02 

2K2=O<rlTIiiO2+2SI2©.  [337] 

On  dissolving  the  resulting  mass  in  water,  and  evaporating  the 
deep  green  solution  thus  obtained  (in  vacuo),  crystals  are  formed 
isomorphous  with  KfO^S02,  in  which  the  hexad  atoms  of  man- 
ganese act  as  acid  radicals,  and  we  call  the  product  potassic 
manganate.  The  acid  corresponding  to  this  compound  has  never 
been  isolated,  and  only  a  few  of  its  salts  are  known.  They  are 
all,  like  potassic  manganate,  exceedingly  unstable. 

On  boiling  a  solution  of  potassic  manganate,  the  following 
remarkable  reaction  results  :  — 


2  -f  3#2<9  -[-  Aq)  = 
M  n08  .  H2O  +  (Kf  Of\_Mn2-\  0,  +  ±K-  0-H+  Aq)  ;  [338] 


and  a  new  compound  called  potassic  permanganate  is  formed,  in 
which  the  atoms  of  manganese  appear  to  have  a  quantivalence 
of  eight.  The  reaction  takes  place  more  readily  if  a  stream  of 
C02  is  passed  through  the  boiling  solution  to  neutralize  the 
1C-  0  -Has  it  forms,  and  when  the  solution  is  not  too  strong  the 
carbonic  anhydride  of  the  atmosphere  will  in  time  determine  the 
same  change  even  at  the  ordinary  temperature.  The  solution 
of  K2=O^Mn20Q  has  a  deep  violet  color,  and  the  changing  tints, 


§333.]  IRON.  377 

during  the  reaction  just  described,  present  a  very  striking  phe- 
nomenon. Hence  the  crude  potassic  manganate,  obtained  by 
melting  together  Mn02  and  K-O-NO^  is  commonly  known  as 
chameleon  mineral;  and  the  production  of  the  characteristic 
green  color,  under  similar  conditions  in  a  blow  -pipe  bead,  is  the 
best  evidence  of  the  presence  of  manganese. 

Potassic  permanganate,  prepared  as  above,  may  be  readily 
crystallized,  and  its  crystals  are  ^omorphous  with  those  of  po- 
tassic perchlorate  ;  that  is,  K2=0^\_Mnz~\^0Q  has  the  same  form 
as  K-0~Cll03.  From  potassic  permanganate  a  number  of  other 
permanganates  may  be  prepared,  and  also  permanganic  acid,  a 
dark-colored  volatile  liquid.  Permanganic  acid  is  formed  when 
the  solution  of  a  manganese  salt  is  boiled  with  nitric  acid  and 
plumbic  dioxide,  and  a  violet  color  developed  in  the  liquid  under 
these  conditions  is  a  certain  indication  of  the  presence  of  man- 
ganese. The  permanganates  are  more  stable  than  the  manga- 
nates,  but  still  they  readily  part  with  a  portion  of  their  oxygen, 
and  act  as  powerful  oxidizing  agents.  A  solution  of  potassic 
permanganate  is  much  used  for  this  purpose  in  the  laboratory. 
For  example,  it  changes  ferrous  into  ferric  salts. 


.  [339] 

The  slightest  excess  of  the  permanganate  is  at  once  indicated  by 
the  color  it  imparts  to  the  liquid,  and  the  reaction  is  the  basis 
of  one  of  the  most  valuable  methods  of  volumetric  analysis. 
Both  the  manganates  and  the  permanganates  are  at  once  de- 
composed by  all  organic  tissues,  which  they  rapidly  oxidize, 
and  a  crude  sodic  permanganate  is  much  used  as  a  disinfecting 
agent. 

333.  IRON.  Fe  =  56.  —  Usually  bivalent  or  quadrivalent, 
but  rarely  sexivalent.  A  universally  diffused  element,  and 
the  most  abundant  and  important  of  the  useful  metals.  As  an 
accessory  ingredient,  it  enters  into  the  composition  of  almost 
every  substance,  and  %it  is  the  chief  metallic  radical  of  a  very 
large  number  of  important  minerals. 


378 


IRON. 


[§333. 


MAGNETITE 

Magnesioferrite 

FRANKLINITE 

HEMATITE 
SPECULAR  IRON 
RED  HEMATITE 
CLAY  IRON  STONE 
RED  OCHRE 

MENACCANITE 
Titanic  Iron 


Limnite 
Xanthosiderite 
Gothite 
LIMONITE 

BROWN  HEMATITE 

BROWN  CLAY  IRON 
STONE 

BOG  ORE 

YELLOW  OCHRE 


SIDERITE 

SPATHIC  IRON 
CLAY  IRON  STONE 
(of  the  coal-beds) 
SPH^ROSIDERITE 

Mesitite 

Ankerite 


Troilite 

Magnetic  Pyrites 
Iron  Pyrites 
Marcasite 
Mispickel 


Oxides. 
Isometric 
Isometric 
Isometric 

Hexagonal, 
Massive, 
Massive, 
Massive, 


Hexagonal. 


Hydrates. 
Massive 
Massive 
Orthorhombic 


ive, 

Massive, 
Massive, 
Massive. 

Carbonates. 
Rhombohedral, 

Massive, 
Concretionary, 
Rhombohedral 
Rhombohedral 

Sulphides. 
Massive 
Hexagonal 
Isometric 
Orthorhombic 
Orthorhombic 


FeS, 
Fe7Ss  or 
FeS<& 


§334] 


IEON. 
Sulphates. 


379 


Hexagonal? 


Hexagonal 


Green  Vitriol  Monoclinic  H^Fe  =  0^  SO  .  Qff2  0, 

Pisanite  Monoclinic       H*[Fe,  Cu]  i  Of  SO  .  6ff20, 

Coquimbite  Hexagonal 

Jarosite  Rhombohedral 


Copiapite 

Raimondite 

Glockerite 

Fibroferrite 

Botryogen 

Voltaite 


Triphylite 

Vivianite 

Dufrenite 

Cacoxenite 

Scorodite 


.  12H20, 
213  .  7H20, 
Massive  05^Fe2]2=02-S02  .  6H20, 

Fibrous          04viu[Jfe2]3x0^[S0J6.  27/^0, 
Monoclinic 


Isometric 


Phosphates  and  Arseniates. 

Orthorhombic 

Monoclinic 

Orthorhombic 

Radiated 

Orthorhombic 


Fe3lOGl(PO)2  .  8J720, 


Pharmacosiderite  Isometric 


Silicates. 
Fayalite  (iron  olivine) 

Orthorhombic? 

Ilvaite  (Yenite)    Orthorhombic     R 
Schorlomite  Massive  Ca^\_Fe2~\ 


.  12ff20, 
e^]  1  06I(  As  0)2  .  4ff2  0, 


[  Ti,Si]6lOz. 


Compare  also  Columbite,  Tantalite,  and  Wolfram  (227)  and 
(253). 

334.  Metallurgy  of  Iron.  —  Native  iron  of  meteoric  origin 
is  not  unfrequently  found,  but  it  i?  doubtful  whether  native  iron 
of  terrestrial  origin  exists,  although  instances  of  its  occurrence 
have  been  reported.  The  commercial  value  of  the  metal  is  so 
small  that  only  those  ferriferous  minerals  which  are  at  the  same 
time  rich,  abundant,  readily  accessible,  and  easily  smelted,  can 
be  utilized  as  ores.  The  useful  ores,  which  are  all  either  ox- 
ides, hydrates,  or  carbonates,  are  distinguished,  in  the  list  of  iron 
minerals  given  above,  by  a  difference  of  type  ;  and  the  names 


380  IRON.  [§334. 

of  the  most  important  varieties  of  the  different  ores  follow  the 
names  of  the  species  to  which  they  belong.  These  ores  are 
found  either  in  veins  or  in  beds,  associated  with  rocks  of  all 
ages  and  of  very  various  characters,  and  the  value  of  a  given  de- 
posit frequently  depends  quite  as  much  on  its  association  with 
coal  and  lime,  and  on  its  proximity  to  a  commercial  centre,  as 
on  the  richness  of  the  ore.  Hence  the  great  wealth,  which  has 
been  drawn  from  the  deposits  of  clay  iron-stone  in  the  coal-beds 
of  England,  an  ore  which,  intrinsically,  is  comparatively  poor. 

All  the  useful  ores  of  iron,  when  not  anhydrous  oxides,  are 
converted  into  this  condition  by  roasting,  and  the  oxides  are 
easily  reduced  to  the  metallic  state  by  simply  heating  the  roasted 
ore  with  coal.  The  smelting  process,  however,  also  involves 
the  fusion  of  the  other  mineral  matter  (gangue),  with  which  the 
true  ore  is  always  mixed.  This  gangue  will  seldom  fuse  by  it- 
self, even  at  the  high  temperature  of  a  blast  furnace,  and  it  is 
almost  always  necessary  to  mix  the  ore  with  some  flux  (usually 
limestone),  which  will  unite  with  the  gangue  and  form  a  fusible 
slag.  The  same  end  is  sometimes  attained,  or  at  least  an  ad- 
vantage is  gained,  by  mixing  different  ores. 

If  the  iron  is  reduced  at  a  comparatively  low  temperature,  as 
in  a  bloomery  forge,  the  metal  separates  from  the  melted  slag  as 
a  loosely  coherent,  spongy  solid,  the  bloom,  and  is  subsequently 
rendered  compact  by  hammering  and  rolling  while  still  at  a 
welding  heat.  If  the  iron  is  reduced  at  a  high  temperature,  as 
in  a  blast  furnace,  the  metal  unites  with  a  small  proportion  of 
carbon  and  is  thereby  rendered  fusible.  Both  the  fused  metal 
and  the  melted  slag  then  drop  together  into  the  crucible  of  the 
furnace,  and  there  the  difference  of  density  determines  a  perfect 
separation  of  the  two  molten  liquids.  The  product  of  the  first 
process  is  nearly  a  pure  metal,  and  is  called  wrought-iron.  The 
product  of  the  second  process  contains  a  variable  amount  of 
carbon  (from  2  to  o  per  cent),  and  is  known  as  cast-iron. 

With  the  outward  aspects  of  these  two  varieties  of  iron  every 
one  is  familiar.  Wrought-iron  is  so  soft  that  it  can  be  readily 
worked  with  files  and  other  steel  tools.  It  is  very  tough,  and 
has  great  tenacity.  It  is  exceedingly  ductile  and  malleable.  It 
readily  fuses  before  a  compound  blow-pipe,  and  in  small  quanti- 
ties may  even  be  melted  in  a  wind-furnace.  It  however  requires, 
for  its  perfect  fusion,  a  full  white  heat.  But  at  a  lower  temper- 


§334.]  IRON.  381 

ature  it  becomes  soft  and  pliable,  and  in  this  condition  can  be 
wrought  or  welded  on  an  anvil.  It  has  a  fibrous  structure,  but 
this  is  in  a  great  measure  due  to  the  mechanical  treatment  it 
receives. 

Cast-iron,  on  the  other  hand,  has  a  granular  or  crystalline 
structure.  It  is  much  harder  than  wrought-iron,  and  propor- 
tionally more  brittle.  It  is  therefore  neither  malleable  nor  duc- 
tile, and  cannot  be  wrought  on  the  anvil  like  the  former  metal ; 
but,  as  it  melts  at  a  much  lower  temperature,  it  is  suitable  for 
castings.  Cast-iron  differs  greatly  in  quality,  and  the  two  ex- 
treme conditions  are  seen  in  the  two  commercial  varieties  known 
as  white  iron  and  gray  iron.  White  iron  has  a  brilliant  white 
lustre  and  a  lamellar  crystalline  fracture,  is  very  brittle,  and  so 
hard  that  it  cannot  be  worked  with  steel  tools.  It  is,  therefore, 
not  suitable  for  casting,  but  may  be  used  to  advantage  for  mak- 
ing wrought-iron  or  steel.  Gray  iron  has  a  darker  lustre  and 
a  more  granular  fracture.  It  is  much  softer,  and  may  be  filed, 
drilled,  or  turned  in  a  lathe.  Although  less  fusible  than  white 
iron,  it  flows  more  freely  when  melted,  and  is  better  adapted 
for  casting.  It  also  contains,  as  a  rule,  less  carbon,  but  the  dif- 
ference of  qualities  seems  to  depend  more  on  the  condition  of 
the  carbon  than  on  the  amount.  In  white  iron  all  the  carbon 
appears  to  be  chemically  combined  with  the  metal,  while  in 
gray  iron  the  greater  part  is  disseminated  in  an  uncombined  form 
through  the  mass.1  A  form  of  white  iron,  called  by  the  Ger- 
mans spiegeleisen  (mirror  iron),  which  crystallizes  in  flat,  bril- 
liant tables,  and  contains  about  five  per  cent  of  carbon,  has 
approximately  the  composition  CFe±,  and  another  crystalline 
variety  has  been  described,  which  nearly  corresponds  to  CFeB ; 
but  the  existence  of  these  compounds  cannot  be  regarded  as 
proved.  Spiegeleisen,  moreover,  is  not  a  pure  ferro-carbide, 
but  always  contains  manganese,  the  amount  varying  from  4  to 
12  per  cent.  Indeed,  manganese  is  a  very  common  ingredient 
of  cast-iron,  as  might  be  anticipated,  seeing  that  manganesian 
minerals  are  so  frequently  associated  with  iron  ores.  Cast-iron 
also  contains  variable  quantities  of  silicon,  sulphur,  and  phos- 

1  When  the  fracture  exhibits  large,  coarse  grains,  among  which  points  of 
graphite  are  distinctly  visible,  the  metal  is  said  to  be  mottled.  Mottled-iron  is 
very  tough,  and  is  especially  valued  for  casting  ordnance.  Of  all  three  vari- 
eties of  cast-iron,  —  the  white,  the  mottled,  and  the  gray.  —  the  iron-masters 
distinguish  several  grades. 


382  IRON.  [§334. 

phorus,  besides  traces  of  other  metals,  such  as  aluminum,  cal- 
cium, and  potassium. 

By  melting  cast-iron  on  the  hearth  of  a  reverberatory  furnace, 
the  carbon  and  the  other  impurities  may  be  more  or  less  thor- 
oughly burnt  out,  and  the  metal  converted  into  wrought-iron. 
At  the  same  time  a  portion  of  the  iron  is  oxidized,  and  a  very 
fusible  slag  is  formed  by  the  union  of  the  oxide  with  the  silica 
always  present. 

The  metal  thickens  as  it  becomes  decarbonized,  and  the 
spongy  bloom  thus  formed  is  easily  separated  from  the  melted 
slag,  and  hammered  or  rolled  into  bars,  as  before  described. 
The  greater  part  of  the  wrought-iron  of  commerce  is  made  in 
this  way,  and  the  process  is  called  "puddling,"  because  the 
melted  metal  is  stirred  or  puddled  on  the  hearth  of  the  fur- 
nace in  order  to  expose  the  mass  more  effectually  to  the  action 
of  the  air.  The  purest  iron,  thus  prepared,  still  contains  a 
small  amount  of  carbon,  which  does  not,  however,  impair  its 
useful  qualities.  The  other  impurities  of  cast-iron,  when  not 
wholly  removed,  render  the  wrought-iron  friable  or  brittle  (short, 
in  technical  language),  and  are  highly  prejudicial.  Sulphur 
makes  the  metal  friable  while  hot  (red  short) ,  while  phosphorus 
and  silicon  make  it  brittle  when  cold  (cold  short). 

That  most  valuable  form  of  iron  called  steel  holds  an  inter- 
mediate position  between  wrought  and  cast  iron,  and  partakes, 
to  a  great  extent,  of  the  valuable  qualities  of  both.  At  a  white 
heat  it  may  be  worked  on  the  anvil,  like  wrought-iron,  and  at 
a  higher  temperature,  but  still,  within  the  range  of  a  wind  fur- 
nace, it  may  be  melted  and  cast.  If  suddenly  quenched  in  water, 
when  red-hot,  it  becomes  as  hard  and  brittle  as  white  cast-iron ; 
and  when  subsequently  heated  to  a  regulated  temperature,  the 
temper  may  be  reduced  to  any  desired  extent.  It  may  thus 
be  made  soft  and  tough,  or  hard  and  elastic,  at  will,  and  on  this 
remarkable  quality  its  numerous  and  important  applications  to 
the  useful  arts  depend.  Good  steel  contains  from  0.7  to  1.7 
per  cent  of  carbon,  and  it  is  made  either  by  carbonizing  wrought- 
iron,  as  in  the  ordinary  cementation  method,  or,  as  in  the  Bes- 
semer process,  by  decarbonizing  cast-iron ;  but  it  is  probable 
that  the  qualities  of  steel  depend  fully  as  much  on  some  un- 
known causes  as  on  the  presence  of  carbon.  It  has  even  been 
doubted  whether  the  presence  of  carbon  is  essential ;  and  indeed, 
the  whole  subject  is  very  obscure. 


§335.]  IRON.  383 

335.  Metallic  Iron.  —  The  Sp.  Gr.  of  the  purest  iron  is  8.14, 
but  cast-iron  has  sometimes  a  specific  gravity  as  low  as  7,  and 
the  density  of  the  different  varieties  of  the  metal  ranges  between 
these  extremes,  the  average  for  good  bar-iron  being  7.7.  Iron 
is  distinguished  for  its  great  susceptibility  to  magnetism,  and  in 
this  respect  it  far  surpasses  both  nickel  and  cobalt,  the  only 
other  metals  that  exhibit  this  property  in  any  marked  degree. 
The  susceptibility  of  iron  to  magnetic  induction  diminishes  as 
its  hardness  increases,  but  at  the  same  time  its  power  of  retain- 
ing the  virtue  is  enhanced.  Thus,  iron  can  only  be  permanently 
magnetized  when  combined  with  carbon,  as  in  steel,  or  with 
oxygen,  as  in  the  magnetic  oxide  or  loadstone,  FeB04,  or  with 
sulphur,  as  in  magnetic  pyrites,  Fe7S8 ;  but  it  is  a  fact  worthy 
of  notice,  that  spiegeleisen,  specular  iron,  Fe203.  and  common 
pyrites,  FeS*  are  almost  indifferent  to  the  action  of  a  magnet, 
and  the  same  is  true  of  most  other  iron  compounds. 

At  a  high  temperature  iron  burns  readily,  and  under  favor- 
able conditions  will  sustain  its  own  combustion  (63).  The 
product  formed  is  Fe30±.  At  a  red  heat  it  also  decomposes 
water,  yielding  the  same  oxide  as  before,  together  with  hydrogen 
gas.  At  the  ordinary  temperature,  however,  polished  iron  re- 
tains its  lustre  unimpaired,  both  in  dry  air  and  in  pure  water 
(free  from  air)  ;  but  when  exposed  to  both  air  and  moisture, 
the  surface  soon  becomes  covered  with  rust.  Moreover,  this 
change  is  not  merely  superficial,  but  under  favorable  conditions 
proceeds  until  the  whole  mass  of  the  metal  is  converted  into  a 
ferric  hydrate,  having  the  composition  of  Limonite.  The  change 
accelerates  as  it  advances,  and  the  rust  first  formed  seems  to 
act  as  a  carrier  of  oxygen  to  the  rest  of  the  metal.  The  cor- 
rosion of  wood  and  other  organic  fibre,  when  in  contact  with 
rusty  nails,  has  been  explained  in  a  similar  way.  It  is  also  a 
favorite  theory  that  a  coating  of  rust  forms  with  the  metal  a 
voltaic  combination,  which  actually  decomposes  the  water  pres- 
ent, and  this  is  thought  to  account  for  the  singular  fact  that  iron- 
rust  always  contains  ammonia. 

Iron  readily  dissolves  in  dilute  mineral  acids,  yielding  a  fer- 
rous salt  and  hydrogen  gas.  It  also  dissolves  in  aqueous  solu- 
tion of  carbonic  acid  if  free  from  air.  Concentrated  sulphuric 
acid,  even  when  boiled  with  iron,  has  but  little  action  upon  it. 
Nitric  acid,  on  the  other  hand,  rapidly  dissolves  the  metal  with 


384  IKON.  [§336. 

evolution  of  NO.  It  is  a  singular  fact,  however,  that  the  most 
concentrated  nitric  acid  (Sp.  Gr.  1.45)  not  only  does  not  attack 
iron,  but  so  modifies  its  condition  that  it  may  subsequently  be 
kept  for  weeks  in  acid  of  the  ordinary  strength  (Sp.  Gr.  not 
less  than  1.35)  without  the  slightest  alteration  of  the  polish  on 
its  surface.  This  same  passive  condition  may  also  be  induced 
in  other  ways. 

Iron  enters  into  chemical  combination  with  almost  all  the 
non-metallic  elements,  and  forms  alloys  with  many  of  the  met- 
als. Corresponding  to  the  three  degrees  of  quantivalence  are 
three  very  distinct  classes  of  compounds :  first,  the  ferrous  com- 
pounds, whose  radical  is  a  single  bivalent  atom  of  iron;  secondly, 
the  ferric  compounds,  having  a  sexivalent  radical  consisting  of 
two  quadrivalent  atoms  of  iron ;  and  lastly,  a  few  very  unstable 
salts  called  ferrates,  analogous  to  the  manganates,  in  which  a 
sexivalent  atom  of  iron  is  the  acid  radical.  The  last  class  of 
compounds,  although  practically  unimportant,  are  interesting, 
as  they  indicate  the  close  relationship  between  iron  and  man- 
ganese ;  but  iron  differs  from  all  the  associated  elements  in  that 
the  two  radicals  Fe=  and  [^2]l  form  equally  stable  compounds, 
and  play  an  equally  important  part  in  the  mineral  kingdom ; 
and  this  double  aspect  of  the  element  is  one  of  its  most  charac- 
teristic and  important  features. 

336.  Ferrous  Compounds.  —  The  crystallized  ferrous  com- 
pounds have,  as  a  rule,  a  light  green  color,,  and  ferrous  oxide 
imparts  the  same  color  to  glass  (152).  The  soluble  ferrous 
salts  have  a  characteristic  styptic  taste.  They  are  isomorphous 
with  the  corresponding  compounds  of  magnesium  and  zinc,  and 
quite  as  closely  allied  to  them  as  to  those  of  manganese,  cobalt, 
and  nickel, —  the  elements  with  which  iron  is  classed  in  the 
scheme  of  this  book.  Thus,  in  nature,  ferrous  carbonate  is  as 
intimately  associated  with  the  carbonates  of  magnesium  and 
zinc  as  with  the  carbonate  of  manganese,  and  the  four  bivalent 
radicals  replace  each  other  in  almost  every  proportion,  not  only 
in  the  carbonates,  but  also  in  the  silicates,  and  in  a  large  num- 
ber of  other  minerals.  In  like  manner,  ferrous  sulphate  (green 
vitriol),  like  the  sulphates  of  the  same  metals,  and  also  those  of 
nickel  and  cobalt,  crystallizes  with  seven  molecules  of  water, 
and  forms  double  salts  with  the  sulphates  of  the  alkaline  metals 
(313),  (322),  (330).  The  sulphate  is  the  most  important  of 


§337.]  IRON.                                         385 

the  soluble  ferrous  salts,  but  all  the  following  are  also  well 
known  :  — 

Ferrous  Chloride  FeCl2  .  ±JT20, 

Ferrous  Nitrate  Fe=Of(N02)2  .  §H20, 

Ferrous  Sulphate  Fe=02=S02  .  (7,  4,  3,  or  2ff20), 

Ferrous  Oxalate  Fe  =  02=  C2  02  .  2  H2  0, 

Ferrous  Phosphate  H2,Fe^ 


In  solutions  of  the  ferrous  salts,  when  protected  from  the  air, 
the  alkaline  hydrates  give  a  white  precipitate  of  ferrous  hydrate, 
Fe  =  OfHft  and  the  alkaline  carbonates  a  similar  white  precipi- 
tate, which  is  a  hydro-carbonate  of  variable  composition.  In 
the  presence,  however,  of  a  large  amount  of  NH±Cl,  neither 
ammonia  nor  ammonic  carbonate  give  any  precipitate,  and  the 
precipitation  by  the  other  alkaline  reagents  is  in  great  measure 
prevented.  The  alkaline  sulphides,  nevertheless,  precipitate 
the  iron  wholly  as  a  hydrated  ferrous  sulphide,  and  so  does  also 
H2S  when  the  solution  is  alkaline,  but  not  when  the  slightest 
excess  of  any  mineral  acid  is  present.  Solutions  of  the  ferrous 
salts,  when  exposed  to  the  air,  absorb  oxygen,  and  the  ferrous 
changes  into  a  ferric  compound.  The  same  is  true  of  the  fer- 
rous precipitates  formed  as  just  described,  all  of  which  are  very 
rapidly  oxidized  as  soon  as  they  are  exposed  to  the  atmosphere. 
The  products  in  any  case  are  determined  by  various  conditions, 
but  the  following  are  some  of  the  most  characteristic  of  the 
reactions  :  — 


+  Aq) 

+  2JJ20  +  Aq).  [340] 


(20Fe-02=S02  -f  Sff20  +  Aq)  +  5(cXe)  =  [341] 

•  3H20)  +  (QlFe.J 


H4.      [342] 

337.   Ferric  Compounds.  —  Ferric  oxide,  when  dissolved  in 
melted  borax,  imparts  to  the  glass  a  yellow  or  yellowish-red 
color,  and  most  of  the  ferric  compounds  affect  the  same-  tints.. 
17  Y 


386  IRON.  [§  337. 

They  are  isomorphous  with  the  corresponding  compounds  of 
aluminium,  and  closely  allied  to  them  in  their  chemical  rela- 
tions. The  following  are  the  most  important  of  the  soluble 
normal  salts:  — 


Ferric  Chloride       [Fez~\lCl6  .  Gff20,  also  with  5  or 

Ferric  Nitrate         [Fea]wg(NOJ6  .  1SH20,  also  with  I2ff20, 

Ferric  Acetate         [^2]1  0^(O2ff3  0)6  -f-  Aq, 

Ferric  Sulphate       [jfoj  I  0^(S02)3  .  $H2  0, 

Diammonic-ferric  Sulphate 


Ferric  Oxalate  [^ej  1  00I(  O2  02)3, 

Sodio-ferric  Oxalate    NaQ,[_Fe2~\  ™  012*n(  C2  02)6  . 


Ferric  acetate  cannot  be  crystallized,  and  the  ferric  salts,  as 
a  rule,  crystallize  with  difficulty.  All  the  well-marked  radi- 
cals of  the  type  [JS2  ]l  manifest  a  very  strong  tendency  to  form 
basic  compounds  (38)  [51],  and  the  ferric  salts  furnish  a  strik- 
ing illustration  of  the  general  principle.  Most  of  the  native 
ferric  salts  are  basic,  and  the  symbols  of  a  number  of  such  com- 
pounds have  already  been  given.  Their  mutual  relations  will 
be  best  understood  if  they  are  studied  in  connection  with  the 
various  hydrates,  from  which  they  may  be  regarded  as  derived, 
and  a  table  of  the  possible  ferric  hydrates  is  easily  made  after 
the  principle  of  (151).  Of  the  compounds  which  are  thus  the- 
oretically possible,  a  large  number  are  easily  prepared,  and  a 
still  larger  number  are  at  times  formed  when  the  conditions 
happen  to  be  favorable  ;  but  as  the  compounds  become  more 
basic,  they  soon  lose  every  trace  of  crystalline  structure,  and 
with  this  all  evidence  of  definite  chemical  constitution  disap- 
pears. The  products  are  then  amorphous  or  colloidal  solids, 
which  present  in  their  composition  every  possible  gradation 
between  certain  limits.1 


1  Solutions  of  various  basic  compounds  are  readily  obtained  either  by  dis- 
solving freshly  precipitated  ferric  hydrate  in  a  solution  of  almost  any  ferric 
salt,  or  by  partially  abstracting  the  acid  of  the  salt  by  the  cautious  addition 
of  an  alkali.  A  solution  of  ferric  nitrate,  for  exaYnple,  may  thus  be  made  to 
take  up  seven  additional  atoms  of  [Fe2].  On  allowing  such  solutions  to  evap- 
orate spontaneously,  the  basic  compounds  may  frequently  be  obtained  in  the 
solid  state. 


§338.]  IRON.  387 

All  the  more  basic  salts  are,  as  a  rule,  insoluble  in  water,  but 
in  several  cases  they  affect  both  a  soluble  and  an  insoluble  mod- 
ification, and  under  certain  conditions  the  first  changes  into  the 
last  on  simply  boiling  the  solution.  The  soluble  condition  ap- 
pears in  all  cases  to  be  a  colloidal  modification,  and  by  dialys- 
ing  (56)  a  solution  of  basic  ferric  chloride  it  is  possible  to 
remove  almost  all  the  acid  radical,  and  obtain  nearly  a  pure 
solution  of  ferric  hydrate.  This  solution  coagulates  on  stand- 
ing, and  the  ferric  hydrate  thus  passes  through  successive  stages 
of  dehydration.  On  boiling  the  water,  the  dehydration  proceeds 
still  further,  until  at  last  a  hydrate  corresponding  to  Gothite  is 
formed.  So  also  the  voluminous  hydrate,  first  precipitated  by 
alkaline  reagents  from  cold  solutions  of  ferric  salts,  undergoes  a 
similar  change  under  the  same  conditions.  These  facts  would 
lead  us  to  infer  that  the  "  coagulation  "  of  the  solutions  of  the 
basic  ferric  salts  is  caused  by  the  elimination  of  a  certain  quan- 
tity of  water  from  the  molecules  of  the  compound. 

The  ferric  compounds,  although  permanent  in  the  air,  are 
easily  reduced  to  the  ferrous  condition  by  the  feeblest  reducing 
agent-;. 


.  [343] 
([^]  CIG+  ff,S+  Aq)  =  S+  (2Fe  C12+  2HCI  +  Aq).  [344] 

In  solutions  of  ferric  salts,  the  alkaline  hydrates  and  carbon- 
ates all  give  a  red  precipitate  of  ferric  hydrate,  whose  constitu- 
tion varies  with  the  conditions  of  the  experiment,  as  indicated 
above.  This  precipitate  is  insoluble  in  an  excess  of  sodic  or 
potassic  hydrate.  In  the  same  solutions  potassic  sulpho-cyanide 
strikes  a  deep  red  color,  and  potassic  ferro-cyanide  gives  a  deep 
blue  precipitate.  These  reactions  are  very  delicate,  and  enable 
us  to  detect  the  smallest  amount  of  a  ferric  compound,  even  in 
the  solution  of  a  ferrous  salt.  The  ferrous  compound,  under 
the  same  conditions,  gives  no  color  and  a  white  precipitate. 

338.  Chlorides.  Fe  C12  and  [7^2]  C76.  —  By  carefully  heating 
crystallized  ferrous  chloride  (336)  out  of  contact  with  the  air, 
the  anhydrous  compound  can  be  obtained;  but  a  solution  of 
ferric  chloride  cannot  be  rendered  anhydrous  by  evaporation, 
since  the  hydrous  compound  is  decomposed  by  heat  into  hydro- 
chloric acid  and  ferric  oxide.  Anhydrous  ferrous  chloride  can 


388  IRON.  [§339. 

also  be*  obtained  by  passing  SIO1  over  ignited  metallic  iron. 
Anhydrous  ferric  chloride  can  be  prepared  in  a  similar  way, 
using  (oJKeJl  instead  of  HKfiJl.  The  first  yields  a  white  subli- 
mate ;  the  second,  which  is  the  most  volatile,  is  deposited  in 
brownish  crystalline  scales,  and  the  Sp.  Gr.  of  its  vapor  has 
been  determined.  There  are  fluorides,  bromides,  and  iodides 
corresponding  to  the  chlorides,  but  they  have  no  special  interest. 

339.  Oxides.  —  FeO,    [^V|03,    Fe^Fe^O*  —  Ferrous 
oxide  may  be  prepared  by  boiling  in  the  surrounding  water  the 
voluminous  white  hydrate  obtained  when  an  alkali  is  added  to 
the  solution  of  a  pure  ferrous  salt,  every  trace  of  air  being  care- 
fully excluded.     If  exposed  to  the  air,  it  rapidly  absorbs  oxy- 
gen, and  \_Fe%\  03  is  the  final  result.     A  black  pyrophoric  pow- 
der, obtained  by  igniting  ferrous  oxalate  in  a  close  vessel,  is  a 
mixture  of  the  same  oxide  with  metallic  iron.     Ferric  oxide  is 
prepared  for  the  arts  by  igniting  green  vitriol,  or  still  better, 
ferric  sulphate.     It  forms,  even  when  most  highly  levigated,  a 
very  hard  powder,  much  used  for  polishing  glass  and  metallic 
surfaces  (Colcothar,  Crocus  Martis,  Rouge).     It  is  also  used  as 
a  red  paint.     Ferrous-ferric  oxide  is  formed  when  either  of  the 
other  oxides  is  intensely  heated  in  the  air,  and  must,  therefore, 
be  regarded  as  the  most  stable  of  this  class  of  compounds.     It 
is  distinguished  by  its  susceptibility  to  magnetism,  and  its  crys- 
talline form  (74),  which  connects  it  with  Spinel  (352)  and 
other  allied  isomorphous  compounds.     Besides  the  above,  one 
or  more  intermediate  oxides  have  been  distinguished,  but  they 
are  probably  mixtures  of  the  oxides  already  named.     As  has 
been  already  stated,  both  the  anhydrous  and  the  hydrous  oxides 
are  abundant  native  minerals,  and  important  ores. 

340.  Sulphides.  —  The  fusible  product  obtained  by  melting 
together  iron  and  sulphur,  and  so  much  used  in  the  laboratory 
for  making  H^S,  is  essentially  ferrous  sulphide,  FeS,  although 
its  composition  is  not  absolutely  constant.     The  same  compound 
may  be  formed  by  mixing  flowers  of  sulphur  and  iron-filings 
with  water,  and,  since  the  resulting  compound  forms  a  coherent 
mass,  this  mixture  is  useful  under  certain  conditions  as  a  ce- 
ment.    Ferric  disulphide,  FeS2  (Iron  Pyrites),  is  by  far  the 
most  abundant  of  the  native  metallic  sulphides.     It  occurs  in 
almost  all  mineral  veins,  and  is  known  to  the  miners  as  Mundic. 
It  is  readily  distinguished  by  its  yellow  color  and  great  hard- 


§341.]  QUESTIONS  AND  PBOBLEMS.  389 

ness.  The  more  compact  varieties  are  very  resisting  minerals, 
but  those  of  a  looser  texture  rapidly  crumble  when  exposed  to 
the  atmosphere,  and  this  is  especially  true  of  the  orthorhombic 
variety  called  Marcasite.  The  crumbling  of  many  rocks  is  also 
caused  by  the  oxidation  of  the  pyrites  which  they  contain.  Al- 
though useless  as  an  ore  of  iron,  common  pyrites  is  exceedingly 
valuable  as  a  source  of  sulphur,  and  for  the  manufacture  of  sul- 
phuric acid.  The  magnetic  sulphide  Fe7S8  has  already  been 
mentioned,  and  there  is  also  a  sulphide,  Fe3S^  corresponding  to 
the  magnetic  oxide,  and  another,  Fe2S3,  corresponding  to  ferric 
oxide.  Moreover,  sulphides  of  the  composition  Fe$S  and  Fe2S 
have  been  formed,  but  it  is  doubtful  whether  they  are  all  defi- 
nite compounds.  The  black  precipitates,  obtained  when  an 
alkaline  sulphide  is  added  to  the  solutions  of  ferrous  and  ferric 
salts,  are  either  sulpho-hydrates  (241)  or  molecular  compounds 
of  the  sulphide  and  water.  They  are  both  very  unstable  prod- 
ucts, and  rapidly  oxidize  when  exposed  to  the  air. 
•  341.  Ferrates. —  Potassic  ferrate,  KfOfFeO^  may  be  pre- 
pared either  by  fusing  ferric  oxide  with  nitre  or  by  passing 
chlorine  gas  through  a  very  strong  solution  of  potassic  hydrate, 
in  which  ferric  oxide  is  suspended.  Both  the  fused  mass  of  the 
first  reaction,  and  the  black  powder  deposited  from  the  alkaline 
solution  in  the  second,  yield  with  water  a  beautiful  violet-col- 
ored solution  of  potassic  ferrate.  This  compound  is  very  un- 
stable, and  has  merely  a  theoretical  interest.  Ferrates  of  the 
alkaline  earths  are  also  known ;  but  neither  ferric  acid  nor  any 
compounds  corresponding  to  the  permanganates  have  as  yet 
been  discovered. 


Questions  and  Problems. 

Manganese. 

1.  By  what  simple  blow-pipe  test  may  the  presence  of  manganese 
in  a  mineral  be  recognized?     How  far  is  the  color  of  the  manganese 
minerals  characteristic  ? 

2.  Compare  the  manganous  with  the  niccolous  and  cobaltous  salts, 
and  show  to  what  extent  they  resemble  each  other,  as  well  as  indi- 
cate the  points  of  difference. 

3.  Compare  the  ammonio-salts  of  the  same  three  elements,  and 


390  QUESTIONS  AND  PEOBLEMS. 

seek  the  cause  of  the  difference  of  the  effects  which  the  atmospheric 
air  produces  when  solutions  of  these  salts  are  exposed  to  its  influence. 

4.  Represent  by  graphic  symbols  the  constitution  both  of  mangan- 
ous  and  manganic  alum. 

5.  Write  the  reaction  of  potassic  hydrate  on  a  solution  of  mangan- 
ous  chloride,  and  the  further  reaction  when  the  resulting  precipitate 
is  exposed  to  the  atmospheric  air.     Assume  that  the  final  product  is 
manganic  hydrate. 

6.  Write  the  reaction  of  hydro-disodic  phosphate  and  ammonic 
hydrate  on  a  solution  of  manganous  chloride,  and  also  indicate  the 
further  change  which  takes  place  on  igniting  the  resulting  precipitate. 

7.  Make  a  list  of  the  oxides  of  manganese,  and  show  how  far  they 
correspond  to  the  oxides  of  nickel  and  cobalt  on  the  one  side,  and 
to  those  of  iron  on  the  other.     Make  also  a  similar  comparison  of  the 
different  hydrates.     Compare  also  the  different  oxides  and  hydrates 
as  regards  their  relative  stability. 

8.  Of  the  metals  thus  far  studied,  which  are  precipitated  from  acid 
solutions,  and  which  only  from  alkaline  solutions,  by  H2S  ? 

9.  By  what  solvents  may  the  sulphides  of  manganese  zinc  and 
cobalt,  when  precipitated  together,  be  separated  ? 

10.  In  what  other  way  may  manganese,  when  in  solution,  be  sep- 
arated from  nickel  and  cobalt  ? 

11.  To  what  relationship  does  the  crystalline  form  of  the  native 
carbonates  of  manganese  point  ? 

12.  By  what  means  may  manganese  be  separated  from  zinc  when 
both  are  present  in  the  same  solution  as  acetates  ?     If  they  are  in 
the  condition  of  chlorides,  how  may  they  be  readily  converted  into 
acetates  V     How  far  may  the  same  methods  be  used  to  separate  man- 
ganese from  the  metallic  radicals  previously  studied  ? 

13.  Write  the  reaction  of  the  atmospheric  oxygen  on  a  solution  of 
ammonio-manganous  chloride. 

14.  Write  the  reaction  of  chlorine  gas  on  manganous  carbonate 
suspended  in  water. 

15.  Represent  by  graphic  symbols  the  constitution  of  Pyrolusite, 
Braunite,  and  Hausmannite,  and  endeavor  to  harmonize  the  crystal- 
lographic  relations  stated  above.     Take  also  into  consideration  the 
relations  of  MnOz  described  in  (236). 

16.  Represent  by  graphic  symbols  the  constitution  of  Manganite 
and  Gothite. 

17.  Write  the  reaction  of  sulphuric  and  also  of  hydrochloric  acid 
on  each  of  the  three  oxides,  MnO^  1/«203,  and 


b 

QUESTIONS  AND  PROBLEMS.  391 

18.  When  a  mixture  of  Mn02  and  oxalic  acid  is  heated  with  di- 
lute sulphuric  acid,  the  products  are  manganous  sulphate  water  and 
carbonic  anhydride  gas.      Write  the  reaction,  and  calculate  how 
much  COZ  would  be  formed  for  every  gramme  of  Mn02  taken. 

19.  Can  you  base  on  the  reaction  just  written  a  method  of  deter- 
mining the  purity  of  the  commercial  "  black  oxide  of  manganese," 
which  is  frequently  a  mixture  of  the  different  native  oxides,  and  is 
sometimes  adulterated  with  sand. 

20.  Assuming  that  one  gramme  of  a  sample  of  the  commercial 
oxide  sets  free,  as  above,  0.654  gramme  of  C02,  how  much  bleaching 
salts  could  be  manufactured  with  1,000  kilos,  of  the  oxide,  assuming 
that  the  symbol  of  the  bleaching  salts  is  (Ca-0)=C72? 

21.  Write  the  reaction  of  MnOz  on  HCl  -f-  Aq,  assuming  that 
MnCl4  is  first  formed  and  subsequently  decomposed  by  the  heat 
employed. 

22.  Represent  by  a  graphic  symbol  the  constitution  of  manganic 
and  manganous  alum.     (332)  and  (352). 

23.  State  the  distinction  between  the  two  classes  of  manganic 
compounds,  and  illustrate  by  representing  the  constitution  of  MnzOa 
first  as  a  normal  sesquioxide,  and  secondly  as  a  molecular  compound 
of  manganous  oxide  and  manganic  dioxide. 

24.  Compare  the  manganic  compounds  with  the  corresponding 
compounds  of  nickel  and  cobalt.     Consider  in  this  connection  the 
relative  stability  of  the  substances  compared. 

25.  Represent  the  constitution  of  potassic  manganate  by  a  graphic 
symbol,  and  compare  this  with  the  graphic  symbol  of  potassic  sulphate. 

26.  How  far  does  the  isomorphism  of  the  sulphates  with  the  man- 
ganates  indicate  the  quanti valence  of  the  metallic  radical  in  these 
compounds  ?     What  should  you  infer  from  the  great  difference  in 
the  stability  of  the  two  classes  of  salts  in  regard  to  the  sexivalent 
condition  of  manganese  ? 

27.  Analyze  reaction  [337],  and  show  that  it  turns  on  a  change 
of  quantivalence  in  the  manganese  atoms. 

28.  Is  it  necessary  to  assume  a  similar  change  of  quantivalence  in 
reaction  [338]  ? 

29.  Represent  the  constitution  of  potassic  permanganate  by  a 
graphic  symbol,  both  on  the  assumption  that  the  atoms  are  octiva- 
lent  and  also  assuming  that  they  are  still  sexivalent.     Can  you  give 
any  reasons  why  one  symbol  should  be  more  probable  than  the 
other  ?     Does  not  the  fact  that  the  permanganates  are  more  stable 
than  the  manganates  have  a  bearing  on  the  question?     How  can 
you  reconcile  the  isomorphism  of  the  permanganates  and  the  per- 


392        •  QUESTIONS  AND  PROBLEMS. 

chlorates,  manganese  being    an    artiad    and    chlorine   a  perissad 
element  ? 

30.  Write  the  reaction  when  a  solution  of  manganous  chloride  is 
boiled  with  free  nitric  acid  and  plumbic  dioxide. 

31.  How  could  reaction  [339]  be  used  to  determine  the  amount 
of  iron  in  a  given  solution  V 

32.  What  do  you  regard  as  the  chief  characteristic  of  manganese 
as  compared  with  the  allied  metallic  radicals  ?  and  why  does  the  study 
of  its  compounds  have  a  peculiarly  important  bearing  on  chemical 
theories  ? 

33.  Does  not  the  study  of  the  manganese  compounds  indicate  a 
more  rational  use  of  the  terminations  ows,  ic,  tie,  and  ate  in  the  no- 
menclature of  chemistry  ? 

34.  How  may  the  principles  of  the  nomenclature  stated  in  Chap- 
ter X.  be  extended  so  as  to  express  accurately  the  constitution  of  the 
more  complex  chemical  compounds  ?     Give  rules  based  on  your  own 
experience,  and  illustrate  them  by  examples.     Bear  in  mind,  how- 
ever, that,  according  to  the  best  usage,  the  Greek  numerals  are  em- 
ployed, rather  than  the  Latin,  as  prefixes. 

Iron. 

35.  Compare  the  native  compounds  of  manganese  and  iron,  and 
point  out  the  analogies  as  well  as  the  differences  which  you  observe. 

36.  Compare  in  the  same  way  the  native  compounds  of  nickel  and 
cobalt  with  those  of  iron,  paying  special  attention  to  the  sulphides 
and  arsenides. 

37.  Compare  the  native  compounds  of  magnesium  and  zinc  with 
those  of  iron. 

38.  The  mineral  Pisanite  indicates  what  relation  between  iron 
and  copper  ? 

39.  Why  is  not  Pyrites  included  among  the  ores  of  iron  ?     State 
some  of  the  circumstances  on  which  the  value  of  a  bed  of  iron  ore 
depends. 

40.  The  Sp.  Gr.  of  Pyrites  is  5.2,  that  of  Marcasite,  4.7,  and  that 
of  Mispickel,  6.2.     Compare  the  atomic  volumes  of  these  minerals. 

41.  Make  a  table  giving  the  symbols  of  the  minerals  isomorphous 
with  Iron  Pyrites  and  Marcasite  respectively. 

42.  Explain  the  theory  of  the  «'  Blast  Furnace,"1  and  show  that 
the  formation  of  slags  of  the  right  fusibility  is  essential  to  the  success 

1  See  Miller's  Chemistry  or  Percy's  Metallurgy 


QUESTIONS  AND  PROBLEMS.  393 

of  the  process,  and  that  the  proportion  of  flux  must  be  differently 
adjusted  according  as  cold  or  hot  blast  is  used. 

43.  The  slag  formed  both  in  the  bloomery  forge1  and  in  the  pud- 
dling process1  is  a  very  fusible  ferrous  silicate,  having  approximately 
the  composition  Fe^O^Si.     Explain  the  theory  of  these  processes, 
and  show  that  the  great  fusibility  of  the  slag  is  an  essential  condition 
of  the  production  of  wrought-iron.     Could  the  loss  of  iron  in  the  slag 
be  avoided  V     How  do  you  account  for  the  low  quantivalence  of  iron 
in  this  product  ?  To  what  mineral  does  it  correspond  in  composition  ? 

44.  Explain  the  theory  of  the  Bessemer  process1  for  refining  cast- 
iron  or  making  steel,  and  compare  it  with  the  puddling  process. 
Consider  especially  the  effects  of  the  very  high  temperature  attained 
in  Bessemer's  converter. 

45.  Compare  together  the  qualities  of  iron  in  its  three  conditions 
of  cast-iron,  wrought-iron,  and  steel. 

46.  State  the^differences  between  the  several  varieties  of  cast-iron, 
gray,  mottled,  white,  and  spiegeleisen. 

47.  When  white  iron  is  dissolved  in  acid,  all  the  carbon  is  con- 
verted into  a  volatile  hydro-carbon  oil,  while  under  similar  circum- 
stances gray  iron  leaves  a  large  residue  of  graphite.     What  conclu- 
sion do  you  draw  from  these  facts  ? 

48.  Write  the  reaction  when  iron  burns. 

49.  Write  the  reaction  when  steam  is  passed  over  red-hot  iron. 

50.  Write  the  reaction  when  iron  rusts,  assuming,  1st.  That  the 
metal  draws  the  oxygen  wholly  from  the  air ;  2d.  That  water  is  de- 
composed and  ammonia  formed. 

51.  Write  the  reaction  of  an  aqueous  solution  of  carbonic  acid  on 
iron,  assuming  that  no  air  is  present.     What  is  the  nature  of  the  solu- 
tion thus  obtained  (279)  ? 

52.  Write  the  reaction  of  dilute  sulphuric  acid  on  iron,  and  in- 
quire how  much  the  acid  should  be  diluted  in  order  to  obtain  the  best 
effect.     In  preparing  ferrous  sulphate,  why  is  it  best  to  use  ferrous 
sulphide  instead  of  metallic  iron  ? 

53.  Write  the  rational  symbol  of  dipotassic-ferrous  sulphate,  and 
compare  its  constitution  with  that  of  the  isomorphous  ferrous  sulphate 
(336). 

54.  Compare  the  sulphates  of  magnesium,  zinc,  manganese,  and 
iron,  as  regards  the  varying  quantities  of  water  of  crystallization 
with  which  the  several  salts  may  combine. 

1  See  Miller's  Chemistry  or  Percy's  Metallurgy. 
17* 


394  QUESTIONS  AND  PKOBLEMS. 

55.  Pure  lerrous  nitrate  may  be  obtained  by  dissolving  ferrous 
sulphide  in  dilute  nitric  acid.     Write  the  reaction. 

56.  When  metallic  iron  is  dissolved  in  dilute  nitric  acid,  the  prod- 
ucts are  ferrous  nitrate,  ammonic  nitrate,  and  water.     Write  the  re- 
action and  compare  it  with  the  last. 

57.  Write  the  reaction  of  nitric  acid  (common  strength)  on  iron, 
assuming  that  the  products  are  feme  nitrate  and  nitric  oxide. 

58.  Point  out  the  ferrous  and  ferric  compounds  among  the  symbols 
on  pages  378  and  379,  and  determine  in  each  case  the  ratio  which 
the  quantivalence  of  the  acid  radical  bears  to  that  of  the  basic  radi- 
cals, both  R=  and  [tfj! 

59.  Ferrous  phosphate  is  formed  by  precipitation  on  adding  com- 
mon sodic  phosphate  to  the  solution  of  a  ferrous  salt.     Write  the 
reaction. 

60.  Ferrous  oxalate  is  obtained  on  adding  ammonic  oxalate  to  a 
solution  of  ferrous  sulphate.     Write  the  reaction.     « 

61.  Write  the  reaction  which  takes  place  when  sodic  hydrate  is 
added  to  a  cold  solution  of  ferrous  sulphate,  the  air  being  wholly  ex- 
cluded.    What  further  change  takes  place  if  the  liquid  is  boiled  in 
which  the  precipitate  is  suspended  ? 

62.  Write  the  reaction  of  ammonic  sulphide  on  a  solution  of  fer- 
rous sulphate,  assuming  that  the  precipitate  fixes  two  molecules  of 
water. 

63.  Write  the  reaction  of  sodic  carbonate  on  a  solution  of  ferric 
sulphate,  assuming  that  the  constitution  of  the  product  is  analogous 
to  that  formed  when  the  same  reagent  is  added  to  a  solution  of  mag- 
nesic  sulphate. 

64.  Write  the  reaction  of  sodic  carbonate  on  a  solution  of  ferrous 
chloride,  first,  when  the  solution  is  cold,  secondly,  when  it  is  boiling. 

65.  Ferric  hydrate  dissolves  in  a  solution  of  acid  potassic  oxalate, 
forming  potassio-ferric  oxalate.    Write  the  reaction.    What  practical 
application  may  be  made  of  it  ? 

66.  Normal  ferric  oxalate  is  precipitated  when  a  slight  excess  of 
any  ferric  salt  is  mixed  with  a  solution  of  ammonic  oxalate.     Write 
the  reaction.     The  precipitated  ferric  oxalate  readily  dissolves  in  a 
solution  of  oxalic  acid.    What  compound  is  probably  formed  ?    When 
this  solution  is  exposed  to  the  sun,  ferrous  oxalate  is  precipitated,  and 
C02  is  evolved.     Write  the  reaction. 

6  7.  A  solution  of  ferrous  carbonate  in  (CV92  -f-  A  q)  deposits,  when 
exposed  to  the  air,  a  hydrate  having  the  composition  of  Limonite. 
Write  the  reaction.  Under  what  circumstances  might  you  expect 


QUESTIONS  AND  PROBLEMS.  395 

that  a  solution  of  ferrous  carbonate  would  be  formed  in  nature,  re- 
membering that  the  soil  contains  more  or  less  ferric  hydrate  ?  Under 
what  circumstances  would  Siderite  be  deposited  from  such  chalybeate 
waters  (279)  ?  Can  you  form  any  theory  which  accounts  for  the 
formation  of  beds  of  Siderite  (clay  iron-stone)  in  connection  with  the 
coal- measures  ? 

68.  Make  a  table  of  the  possible  ferric  hydrates,  and  point  out  the 
relations  of  the  native  hydrates  in  your  scheme. 

69.  By  means  of  the  table  made  as  just  directed,  show  in  what  re- 
lation the  different  native  sulphates,  phosphates,  and  arseniates  stand 
to  the  hydrates. 

70.  Make  a  table  illustrating  how  many  nitrates,  sulphates,  or 
phosphates  may  be  formed  corresponding  to  any  one  of  the  possible 
hydrates. 

71.  Represent  by  graphic  symbols  the  constitution  of  the  basic 
sulphate  O^Fe^OfSOr 

72.  When  to  the  solution  of  a  ferric  salt  an  alkali  is  added  until 
it  begins  to  occasion  a  permanent  precipitate,  and  the  solution  is 
then  raised  to  the  boiling  point,  the  whole  or  the  greater  part  of  the 
iron  is  precipitated  as  an  insoluble  basic  salt.     How  do  you  explain 
the  reaction  ? 

73.  Starting  with  a  molecule  of  a  ferric  salt,  show  what  products 
would  result  by  the  assimilation  of  successive  molecules  of  ferric 
hydrate.     Again,  starting  with  one  or  more  of  the  complex  mole- 
cules thus  obtained,  and  eliminating  all  the  possible  molecules  of 
water,  show  what  must  be  the  constitution  of  the  basic  salts  which 
would  then  be  formed. 

74.  Have  you  observed  that  the  solubility  of  salts  in  water  has 
any  connection  with  the  number  of  atoms  of  typical  hydrogen  they 
contain  ?     Cite  -examples  in  favor  of  this  theory. 

75.  Cite  different  cases  in  which  water  is  eliminated  from  a  mole- 
cule on  boiling  the  liquid  in  which  the  compound  is  dissolved  or 
suspended. 

76.  When  anhydrous  ferrous  sulphate  is  heated  to  redness,  as  in 
the  process  of  making  Nordhausen  sulphuric  acid  (249),  it  is  resolved 
into  ferric  oxide  and   into  sulphurous  and   sulphuric  anhydrides. 
Write  the  reaction. 

77.  The  Nordbausen  acid  is  now  more  frequently  made  by  distil- 
ling anhydrous  ferric  sulphate.     Write  the  reaction,  and  show  how 
the  sulphate  may  be  regenerated  and  the  same  oxide  used  over  and 
over  again. 


396  QUESTIONS  AND  PROBLEMS. 

78.  How  could  the  reactions  [343]  and  [339]  be  used  to  deter- 
mine the  relative  amounts  of  the  two  iron  radicals  in  a  given  mineral, 
assuming  that  it  could  be  brought  into  solution  without  changing  the 
atomic  condition  of  the  metal ? 

79.  Baric  carbonate  precipitates  all  the  iron  from  ferric,  but  not 
any  of  the  metal  from  ferrous  solutions.     Moreover,  ferrous  hydrate 
precipitates  ferric  hydrate  from  the  solutions  of  ferric  salts.     Write 
these  reactions,  and  discuss  the  different  relations  of  the  two  iron  rad- 
icals to  which  they  point. 

80.  By  what  characteristic  reactions  may  the  atomic  condition  of 
iron,  when  in  solution,  be  easily  determined  ? 

81.  Can  one  condition  of  iron  be  said  to  be  more  stable  absolutely 
than  the  other? 

82.  What  two  wholly  distinct  relationships  does  iron  manifest? 
Trace  the  lines  of  connection  in  each  case.     Point  out  also  the  spe- 
cific characters  by  which  iron  is  related  to  each  member  of  the  two 
groups  of  allied  elements. 

83.  By  what  character  are  the  elements  classed  with  aluminum 
chiefly  marked  ? 

84.  Compare  the  reaction  of  (HCl  -f-  Aq)  on  Ni^0v  Co203,  Mn20^ 
FezOy  and  show  that  the  differences  depend  on  the  relative  stability 
of  the  several  hexad  radicals. 

85.  In  what  way  may  magnesium,  zinc,  nickel,  cobalt,  and  man- 
ganese be  separated  from  aluminum,  chromium,  and  iron  ? 

86.  Is  there  any  reason  for  believing  that  in  crystallized  ferric 
chloride  the  water  forms  a  part  of  the  salt  molecule  ?     Write  the 
reaction  which  takes  place  when  the  salt  is  heated. 

87.  Does  the  Sp.  Gr.  of  anhydrous  ferric  chloride  throw  any  light 
on  the  constitution  of  the  ferric  salts  ? 

88.  Write  the  reactions  of  HIOl  and  of  @1-@1  on  ignited  metallic 
iron.     Why  should  a  ferrous  compound  be  formed  in  the  first  case 
when  a  ferric  compound  is  formed  in  the  second  ? 

89.  When  MnOz  is  melted  into  glass  colored  green  by  ferrous  ox- 
ide, the  color  is  either  wholly  removed,  or,  when  originally  very  deep, 
is  changed  to  yellow.     How  do  you  explain  this  reaction,  and  also 
the  other  familiar  blow-pipe  reactions  of  ferric  oxide  with  a  borax 
bead. 

90.  Ferric  oxide,  obtained  by  drying  the4iydrate  at  a  temperature 
not  exceeding  320°,  dissolves  easily  in  acids;  but  if  heated  to  a  low 
red  heat,  it  suddenly  glows,  becomes  denser,  and  after  this  dissolves 
in  acids  with  difficulty.     Are  you  acquainted  with  similar  facts  in 


QUESTIONS  AND  PROBLEMS.  397 

regard  to  any  other  metallic  oxides  ?  It  is  observed  that  the  ignited 
oxide  dissolves  without  difficulty  in  (HCl  -j-  Aq)  when  the  action  is 
aided  by  ferrous  chloride,  zinc,  stannous  chloride,  or  some  other  re- 
ducing agent.  How  do  you  explain  the  reaction  ? 

91.  Write  the  reaction  when  FeSz  is  burnt  in  a  current  of  air,  as- 
suming that  the  products  are  Fez03  and  *S02,  and  calculate  how 
much  sulphuric  acid,  Sp.  Gr.  1.501,  can  be  made  from  1,000  kilos, 
of  Pyrites. 

92.  In  one  process  of  purifying  coal  gas,  the  HZS  is  absorbed  by 
moist  ferric  oxide,  and  the  sulphide  thus  formed  is  subsequently 
exposed  to  the  air,  when  the  oxide  is  "  regenerated."    Explain  the 
reaction. 

93.  Pyrites  appears  to  be  formed  in  nature  by  the  deoxidation  of 
calcic  sulphate,  by  means  of  organic  matter  in  presence  of  chalybeate 
waters,  and  crystals  have  been  formed  artificially  on  twigs,  in  solu- 
tions of  ferrous  sulphate.     Explain  the  reaction. 

94.  When  S02  is  passed  through  an  alkaline  solution  of  potassic 
ferrate,  ferric  oxide  is  precipitated,  while  potassic  sulphate  is  formed 
in  the  solution.     Write  the  reaction,  and  show  that  it  may  be  used 
to  determine  the  constitution  of  the  ferrates. 

95.  The  slag  of  a  blast-furnace  is  essentially  a  double  silicate  of 
aluminum  and  calcium,  in  which  the  atomic  ratio1  of  the  two  basic 
radicals,  Ca=  and  [-4/,]l,  is  one  to  two.     In  the  less  fusible  slags  the 
total  quantivalence  of  all  the  basic  radicals  is  equal  to  that  of  the  sil- 
icon, while  in  the  most  fusible  slags  it  is  only  one  half  of  that  amount. 
Write  the  symbols  of  these  silicates,  assuming  (as  is  usually  the  case) 
that  the  calcium  is  partially  replaced  by  magnesium  and  iron. 

1  By  the  atomic  ratio  of  a  compound  is  meant  the  ratio  between  the  total 
quantivalence  of  the  several  radicals  which  it  contains. 


398  CHROMIUM.  [§342 


Division  XII. 

342.  CHROMIUM.    Cr  =  52.2.  —  Sometimes,   although 
rarely,  bivalent.     Usually  either  quadrivalent  or  sexivalent. 
Many  of  the  compounds  of  this  element  have  a  brilliant  color, 
and  are  used  as  paints,  and  the  name  is  derived  from  xP°>P-a 
(color).     The  only  important  native  compounds  are 

Chromite  (Chrome  Iron)     Isometric       .Fe,[O2]vm04, 
Crocoite  Monoclinic    Pb=02=Cr02. 

The  first  is  the  ore  from  which  all  the  chrome  pigments  used  in 
the  arts  are  indirectly  prepared.  It  has  an  iron-black  color, 
and  has  been  found  in  abundance  at  a  few  localities,  associated 
with  serpentine.  The  second,  although  a  very  rare  mineral,  is 
well  known  on  account  of  its  brilliant  red  color,  and  in  it  the 
element  chromium  was  first  discovered  (by  Vauquelin  in  1797). 

343.  Metallic  Chromium  may  be  prepared  by  reducing  Cr.203 
with  carbon  at  a  very  high  temperature,  and  still  more  readily 
by  reducing  Or.2Cl6  with  zinc,  magnesium,  or  the  alkaline  metals. 
On  account  of  its  very  great  infusibility,  it  has  never  been  ob- 
tained in  compact  masses,  and  its  qualities  are  therefore  imper- 
fectly known.     The  whitish-gray  porous  mass,  formed  when  the 
oxide  is  reduced  by  carbon,  has  a  Sp.  Gr.  of  5.9.     It  is,  like 
cast-iron,  a  combination  of  the  metal  with  carbon,  and  consists 
of  grains,  which  are  as  hard-  as  corundum.     The  crystalline 
powder,  obtained  by  reducing  the  chloride  with  zinc,  has  a  Sp. 
Gr.  of  6.81,  and  is  undoubtedly  a  purer  condition  of  the  metal. 
When  in  fine  powder,  chromium  takes  fire  below  redness ;  but 
in  its  more  compact  forms  it  resists  oxidizing  agents  as  well  as 
aluminum,  and  acts  towards  the  different  mineral  acids  in  a 
similar  way. 

344.  Chromous  Compounds.  —  This  class  includes  all  those 
compounds  of  chromium  in  which  the  element  is  bivalent ;  but, 
since  its  atoms  in  this  condition  have  still  four  strong  affinities 
unsatisfied,  the  compounds  of  this  order  are  all  very  unstable. 
The  most  important  is  CrCl^  which  is  obtained  by  heating 
Cr2Cle  to  redness  in  a  current  of  dry  hydrogen.     The  white 
powder  thus  formed  gives  a  blue  solution  with  water,  which, 
however,  rapidly  absorbs  oxygen,  and  becomes  green  when  ex- 


§  345.]  CHROMIUM.  399 

posed  to  the  air.  Chromous  hydrate,  which  falls  as  a  dark  brown 
precipitate  on  adding  caustic  potash  to  the  blue  solution,  even 
decomposes  water  with  evolution  of  hydrogen.  The  most  stable 
of  the  chromous  salts  is  K2,CnOf[SO,']2  .  6//20,  which  forms 
beautiful  blue  crystals  isomorphous  with  the  corresponding  fer- 
rous salt. 

345.  Chromic  Compounds.  —  In  these  compounds  the  ele- 
ment is  quadrivalent,  but  they  all  contain  the  sexivalent  radical 
[  (7rJ.  The  commercial  chromic  oxide  is  a  brilliant  green  pow- 
der, which  is  very  much  used  in  the  arts,  not  only  as  a  common 
paint  (chrome  green),  but  also  as  a  vitritiable  pigment,  since  it 
imparts  a  beautiful  green  color  to  glass  and  to  the  glazing  of 
porcelain  ware.  It  may  be  prepared  from  the  chromates  in  a 
great  variety  of  ways,  as  is  illustrated  by  the.  following  re- 
actions :  — 

4[HgJ=O/CrOa  =  2[CrJO8  +  SHIg  +  5©=©.  [345] 
(NH4)/0./Cr205  =  [CrJOs  +  4IU2©  +  SMST.  [346] 

4Oii©a,oia  =  2[Cr2]io3  +  4®K9i  +  ©=©.  [347] 

K2  0/Cr.Os  +  01-01  = 

[CrJiO.  +  2KC1  +  2(o)=CD.  [348] 

The  first  two  reactions  are  obtained  by  simply  igniting  the  solid 
chromates.  The  third,  by  passing  the  vapor  of  chloro-chromic 
anhydride  through  a  red-hot  porcelain  tube,  and  the  last,  by 
passing  chlorine  gas  over  ignited  potassic  dichromate.  By  the 
third  reaction  the  oxide  may  be  obtained  in  definite  rhombohe- 
dral  crystals  (Sp*  Gr.  5.21),  which  have  the  form  and  hardness 
of  specular  iron,  and  even  the  amorphous  commercial  oxide  is 
so  hard  that,  when  finely  levigated,  it  may  be  used  like  rouge 
for  polishing  glass.  In  this  hard  condition  the  oxide  is  almost 
insoluble  in  acids.  There  is,  however,  a  less  dense  condition  of 
the  oxide  (obtained  by  cautiously  heating  the  hydrate),  which 
dissolves  freely  in  all  the  mineral  acids.  It  has  a  darker  color, 
and,  like  ferric  oxide,  changes  suddenly  with  incandescence  into 
the  insoluble  modification,  if  heated  above  a  definite  point.  At 
the  highest  temperatures  chromic  oxide  does  not  lose  oxygen, 
and  cannot  be  reduced  by  hydrogen.  It  may  be  melted  by  the 
heat  of  a  forge  fire,  and  the  molten  oxide  forms,  on  cooling,  a 
very  hard  dark-green  crystalline  solid. 


400  CHROMIUM.  [§345. 

There  are  a  number  of  chromic  hydrates  corresponding  to  the 
ferric  hydrates  ;  but  the  different  compounds  cannot  be  isolated 
as  readily,  and  their  symbols  have  not  been  as  accurately  deter- 
mined. When  sodic  or  potassic  hydrate  is  added  to  the  solu- 
tion of  a  chromic  salt,  the  chromic  hydrate  first  precipitated  is 
dissolved  by  an  excess  of  the  reagent,  but  the  precipitate  reap- 
pears on  boiling  the  liquid.  These  precipitates  retain  a  portion 
of  the  alkali,  which  modifies  the  qualities  of  the  hydrate,  and 
this  circumstance  renders  the  investigation  of  these  compounds 
very  difficult.  The  only  way  to  procure  a  pure  hydrate  is  to 
precipitate  with  ammonia  from  boiling  solutions.  The  light- 
blue  precipitate  thus  obtained  retains  from  one  to  seven  mole- 
cules of  water,  according  to  the  conditions  under  which  it  is 
dried.  * 

The  soluble  chromic  salts  affect,  as  a  rule  at  least,  two  modi- 
fications. In  one  state  they  have  a  violet  color,  and  crystallize 
more  or  less  readily,  while  in  the  other  they  have  a  green  color, 
and  are  uncrystallizable.  Thus  we  have,  besides  an  anhydrous 
chromic  sulphate,  which  is  red  and  insoluble,  the  two  following 
hydrous  salts  :  — 


Violet  Sulphate  (soluble  and  cryst.)     [Cr^W^SO.^  .  15ff20, 
Green        «      (soluble  but  uncryst.)   [OJ  1  0^(S02)8  .    5R20. 

The  second  is  obtained  by  heating  the  crystals  of  the  first  to 
100°.  But  the  water  thus  driven  off  cannot  be  wholly  water  of 
crystallization,  for  on  simply  boiling  a  solution  of  the  violet 
compound  the  same  change  of  color  and  crystalline  character 
takes  place.  There  is  evidently  an  essential  alteration  in  the 
molecular  structure  of  the  compound,  but  further  than  this  we 
have  as  yet  no  knowledge. 

The  best  known  of  the  chromic  salts  is  chrome  alum,  which 
is  easily  prepared  from  commercial  potassic  bichromate  by  the 
reaction. 

BS02  +  Ag)  = 

H,0  +  Aq).  [349] 


This  salt,  like  the  other  alums,  crystallizes  with  24^0  in  octa- 
hedrons having  a  dark  purple  (nearly  black)  color,  but  which, 
when  sufficiently  thin,  transmit  a  beautiful  ruby  red  tint.  Care 


§348.J  CHROMIUM.  401 

must  be  taken  in  reducing  the  chromate  that  the  temperature 
of  the  solution  does  not  rise  too  high,  for  above  70°  or  80°  the 
change  above  described  takes  place,  and  the  salt  loses  its  power 
of  crystallizing.  By  keeping,  however,  the  green  solution  thus 
formed  for  several  weeks,  it  gradually  recovers  its  violet  color, 
and  then  will  yield  the  normal  crystals. 

346.  The  Chromic  Oxalates  form  two  interesting  series  of 
double  salts.     Those  of  the  first  class  have  a  dark-blue,  and 
those  of  the  second  class  a  ruby-red  color.     Thus  we  have 

Blue  Salt  K*\_  O2]  «u  0^(  O2  02)6 .  Gff2  0, 

Red  Salt  7T2,[ O2] ™ #8viii( <?2 02)4 .  8ff2 Oorl2ff20. 

Ammonia  gives  no  precipitate  in  solutions  of  these  salts,  neither 
does  potassic  hydrate,  until  they  are  boiled.  Corresponding 
compounds  are  known  containing  (Nff^)2,  Na2,  Ba,  Sr,  Ca,  or 
Mg  in  place  of  7T2,  but  with  varying  quantities  of  water  of  crys- 
tallization. 

347.  Chromic  Nitrate  may  be  obtained  in  dark  purple  crys- 
tals having  the  composition  [O2]i0J(^02)e  .  18^0,  by  dis- 
solving chromic  hydrate  in  nitric  acid,  but  the  solution  becomes 
green  and  uncrystallizable  if  heated  beyond  a  limited  degree. 

348.  Chromic  Chloride,  [OJ  1(7/6,  is  prepared  by  passing 
chlorine  gas  through  an  intimate  mixture  of  chromic  oxide  with 
carbon,  heated  to  intense  redness  in  a  crucible  [126],  when  the 
chloride  sublimes  and  may  be  condensed  in  a  second  crucible 
covering  the  mouth  of  the  first.     It  forms  nacreous  scales  which 
have  a  beautiful  peach-blossom  color,  and  resist  the  action  of 
the  strongest  acids.    They  are  insoluble  in  cold  water,  and  even 
in  boiling  water  only  dissolve,  if  at  all,  very  slowly ;  but  singu- 
larly, on  the  addition  of  the  smallest  quantity  of  chromous  chlo- 
ride, they  dissolve  immediately,   generating  much  heat,  and 
forming  a  green  solution  identical  with  that  obtained  by  dissolv- 
ing chromic  hydrate  in  hydrochloric  acid.     A  solution  of  the 
corresponding  violet  chloride  may  be  formed  by  adding  baric 
chloride  to  a  solution  of  the  violet  sulphate  ;  and  it  is  worthy  of 
notice  that,  while  from  this  last  solution  argentic  nitrate  precip- 
itates the  whole  of  the  chlorine,  it  only  precipitates  from  a  so- 
lution of  the  green  compound  one  third  of  its  chlorine,  unless 
the  liquid  is  boiled.     Green  crystals  having  the  composition 

z 


402  CHROMIUM.  [§349. 

[  (7r2]  016  •  12^0  have  been  described,  and  compounds  of  chro- 
mic chloride  with  the  alkaline  chlorides  are  also  known. 

Besides  the  remarkable  modifications  of  the  chromic  salts  de- 
scribed above,  most  of  them  manifest  a  strong  tendency  to  form 
basic  compounds,  but  the  principle  which  they  illustrate  has 
been  already  sufficiently  discussed  (337). 

349.  Chlorhydrines.  —  When  hydrated  chromic  chloride  is 
dried,  it  gives  off,  as  the  temperature  increases,  both  water  and 
hydrochloric  acid,  and  compounds  are  formed  which  occupy  an 
intermediate  position  between  chromic  chloride  and  chromic 
hydrate,  and  may  be  regarded  as  derived  from  the  former  by 
replacing  one  or  more  atoms  of  chlorine  with  hydroxyl.  Thus 
we  have 

Chromic  Chloride  [<7r2]IC?6, 

Chromic  Penta-chlorhydrine  [O2]1C76  ,  Ho  . 

Chromic  Tetra-chlorhydrine  [  O2]  1  014  ,  Ho? 

Chromic  Dichlorhydrine  [  <7r2]IC7a  ,  Ho^ 

Chromic  Hydrate 


The  name  chlorhydrines  is  now  generally  applied  to  bodies 
of  this  class,  and  it  can  easily  be  seen  that  they  may  be  formed 
from  water  and  the  anhydrous  chlorides  by  a  simple  metathesis. 
The  compounds,  whose  symbols  are  given  in  (225)  and  (263), 
may  be  regarded  as  having  a  similar  constitution,  and  the  same 
is  true  of  many  other  oxy  chlorides,  oxyfluorides,  &c. 

350.  Chromates  or  Compounds  in  which  Chromium  is  Sexiv- 
alent.  —  These  are  the  most  characteristic  and  important  of  the 
compounds  of  this  element,  and  the  best  known  of  all  is  potassic 
dichromate,  which  is  manufactured  on  a  large  scale  in  the  arts, 
and  extensively  used  both  in  dyeing  and  in  the  preparation  of 
various  chrome  pigments.  It  is  made  from  native  chrome  iron, 
which  is  reduced  to  fine  powder  and  roasted  on  the  hearth  of  a 
reverberatory  furnace  with  a  mixture  of  chalk  and  potassic  car- 
bonate. The  mixture  is  constantly  stirred  to  hasten  the  oxida- 
tion, and  the  chalk  facilitates  the  change  by  retaining  the  mass 
in  a  porous  condition.  From  the  product,  water  dissolves  yel- 
low potassic  chromate,  which  is  easily  converted  into  the  red 
dichromate  by  the  addition  of  nitric  acid,  and  the  salt  is  then 


§  350.]  CHROMIUM  403 

separated  and  purified  by  repeated  crystallizations.  There  are 
three  potassic  chromates,  all  of  which  yield  anhydrous  crystals 
easily  soluble  in  water. 

Potassic  Chromate  (Yellow)  KfOfCrO^ 

Potassic  Bichromate  (Orange  Red)          K^O^Cr20^ 
Potassic  Trichromate  (Dark  Red)  K^OfCr308. 

The  normal  salt  is  isomorphous  with  potassic  sulphate.  It 
melts  when  heated,  and  is  not  decomposed  by  simple  ignition  ; 
but  when  heated  with  reducing  agents  it  yields  chromic  oxide 
mixed  with  some  potassic  salt.  When  in  solution,  it  has  an 
alkaline  reaction,  and  is  converted  into  the  dichromate  by  the 
weakest  acids.  The  dichromate  also  fuses  without  decomposi- 
tion, but  when  heated  to  a  high  temperature  it  is  converted  into 
the  normal  salt  and  chromic  oxide.  In  solution  it  has  an  acid 
reaction,  and  on  the  addition  of  potassic  hydrate  changes  to  the 
normal  salt.  Both  salts  possess  great  coloring  power.  The 
trichromate  has  merely  a  theoretical  interest. 

In  another  process  of  manufacturing  the  commercial  chro- 
mates the  chrome  ore  is  simply  roasted  with  lime.  There  is 
thus  formed  the  normal  calcic  chromate,  which,  although  itself 
only  partially  soluble  in  water,  is  converted  by  digestion  with 
dilute  sulphuric  acid  into  a  dichromate,  which  is  very  soluble, 
and  from  this  solution  the  other  chromate  may  be  easily  obtained 
by  simple  metathetical  reactions.  The  chromates  both  of  cal- 
cium and  strontium  dissolve  readily  in  dilute  acetic  acid,  while 
baric  chromate  is  insoluble  in  this  reagent ;  and  on  this  fact  is 
based  an  important  method  of  qualitative  analysis. 

There  are  two  plumbic  chromates,  which  are  not  only  impor- 
tant pigments  and  dyes,  but  are  also  interesting  theoretically. 
Their  symbols  are  usually  written  thus :  — 

Plumbic  Chromate  (Chrome  Yellow)        Pb=02=Cr02, 
Diplumbic      "         (Chrome  Orange)         (Pb-0-PbyOfCrO^ 

The  first  falls  as  a  brilliant  yellow  precipitate  when  a  soluble 
chromate  is  added  to  a  solution  of  plumbic  acetate,  and  corre- 
sponds to  the  mineral  Crocoite.  It  melts  at  a  moderate  heat, 
forming  on  cooling  a  red  crystalline  solid ;  but  when  strongly 
ignited  it  is  decomposed,  and  a  mixture  of  the  second  compound 


404  CHROMIUM.  [§  350. 

with  chromic  oxide  is  the  result.  The  diplumbic  chromate  has 
a  deep  orange  or  red  color,  according  to  the  mode  of  prepara- 
tion. The  finest  vermilion-red  is  made  by  fusing  the  yellow 
chromate  with  nitre,  and  washing  out  the  potassium  salt  with 
water,  while  an  orange  color  is  obtained  in  dyeing  by  passing 
the  cloth  through  boiling  lime-water,  after  chrome  yellow  has 
been  fixed  in  its  fibres  by  steeping  it  successively  in  solutions 
of  plumbic  acetate  and  potassic  bichromate. 

Several  other  metallic  chromates,  which  are  easily  prepared 
by  precipitation,  are  used  in  painting ;  but  the  coloring  power 
of  the  chrome  pigments  is  so  great  that  they  are  frequently 
adulterated  with  chalk  or  some  similar  white  material,  and  the 
tint  is  varied  by  mixing  them  with  other  paints.  One  variety 
of  chrome  green  is  a  mixture  of  chrome  yellow  with  Prussian 
blue. 

The  chromates  are  oxidizing  agents,  and  fused  plumbic  chro- 
mate is  sometimes  used  for  this  purpose  in  organic  analysis. 
When  heated  with  strong  sulphuric  acid  they  evolve  oxygen  gas 
[230] ;  with  hydrochloric  acid  they  evolve  chlorine,  and  in  both 
cases  chromic  salts  are  formed. 

From  the  chromates  we  can  easily  prepare  chromic  anhydride, 
CrOB,  and  the  comparative  stability  of  this  compound  illustrates 
most  markedly  the  chief  characteristic  of  the  element  chromium. 
The  anhydride  is  most  readily  obtained  by  pouring  one  meas- 
ure of  a  saturated  solution  of  potassic  dichromate  into  one  and 
a  half  measures  of  concentrated  sulphuric  acid.  As  the  liquid 
cools,  chromic  anhydride  crystallizes  from  it  in  splendid  crim- 
son needles.  This  beautiful  compound  is  permanent  in  the  air, 
and  melts  at  190°  without  undergoing  decomposition ;  but  at  a 
higher  temperature  it  gives  off  oxygen  gas,  changing  first  into  an 
intermediate  brown  oxide,  CrsO&  and  afterwards  into  Cr203. 
It  deliquesces  in  moist  air,  and  dissolves  in  water  in  all  propor- 
tions. This  solution  may  be  regarded  as  chromic  acid,  but  the 
solution  on  evaporation  yields  crystals  of  the  anhydride,  and  we 
have  no  evidence  that  a  definite  compound  is  formed.  It  is  a 
very  powerful  oxidizing  agent,  and  absolute  alcohol  inflames 
when  brought  in  contact  with  the  crystals. 

Chlorochromic  Anhydride,  GrW^Cl^  a  compound  of  the 
same  type  as  the  last,  is  distilled  when  a  mixture  of  potassic 
dichromate,  common  salt,  and  sulphuric  acid  is  heated  in  a  glass 


§351.]  CHROMIUM.  405 

retort.  It  is  a  blood-red  volatile  liquid,  boiling  at  118°,  and 
yielding  a  vapor  whose  0p.  (J$r..  (5.52)  can  be  easily  determined. 
It  is  at  once  decomposed  by  water  into  hydrochloric  acid  and 
chromic  anhydride,  and,  like  the  last,  is  a  powerful  oxidizing 
agent ;  but  it  is  chiefly  interesting  from  its  theoretical  bearings. 
The  existence  also  of  GrCl^  and  CrCl4  has  been  inferred  from 
certain  reactions,  but  they  have  never  been  isolated. 

When  potassic  dichromate  is  dissolved  in  moderately  strong 
hydrochloric  acid  at  a  gentle  heat,  there  separate,  on  cooling, 
beautiful  orange-colored  needles,  of  a  salt  whose  composition 
rn;iy  be  represented  by  the  symbol  GrlO^Cl.Ko  or  K-Q-(On 
02,  C7),  and  another  compound  has  been  obtained  whose  symbol 
las  been  written  Crl0.2,Cl,Ho  .  2ff20l.  Their  theoretical  re- 
lations are  obvious. 

Another  interesting  compound  belonging  to  the  type  of  chro- 
mic anhydride  is  the  fluoride,  CrF6.  It  distils  when  a  mixture 
of  fluor-spar,  plumbic  chromate,  and  sulphuric  acid  are  heated 
in  a  leaden  retort,  and  may  be  condensed  (in  a  perfectly  dry 
leaden  receiver  kept  at  a  very  low  temperature)  to  a  blood-red 
liquid;  but  the  moment  it  comes  in  contact  with  moist  air  it  is 
decomposed  into  hydrofluoric  acid  and  chromic  anhydride,  and 
this  reaction  is  one  means  of  preparing  the  anhydride  in  a  state 
of  purity. 

Lastly,  there  appears  to  be  a  perchromic  acid  corresponding 
to  the  permanganic  acid.  The  compound  in  question  is  formed 
when  to  a  solution  containing  peroxide  of  hydrogen  and  free 
hydrochloric  or  sulphuric  acid  is  added  a  small  quantity  of  some 
chromate.  On  shaking  up  the  mixture  with  a  few  drops  of 
ether,  this  solvent  acquires  a  deep  blue  color,  which  is  supposed 
to  be  due  to  perchromic  acid,  and  the  reaction  serves  as  a  very 
delicate  test  for  chromium. 

351.  Sulphides.  —  The  sulphides  of  chromium  are  unimpor- 
tant. The  black  precipitate  formed  when  ammonic  sulphide  is 
added  to  the  solution  of  a  chromous  salt  is  probably  CrS.  A 
sesquisulphide,  Or2SB,  may  also  be  obtained  as  a  black  powder 
by  passing  ff2S  over  ignited  Cr2Cl6.  Like  aluminic  sulphide, 
it  is  decomposed  by  water,  and  cannot,  therefore,  be  formed  in 
an  aqueous  solution. 


406  QUESTIONS  AND  PROBLEMS. 

Questions  and  Problems. 

1.  In  what  order  would  you  classify  the  elements  allied  to  chro- 
mium, regarding  only  the  stability  of  the  compounds  in  which  they 
act  as  bivalent  radicals  ?     Make  a  table  illustrating  this  point. 

2.  In  what  order  would  you  classify  the  same  elements,  regarding 
alone  the  stability  of  the  several  radicals  [jR2]l  V     Compare  the  qual- 
ities of  the  several  oxides  and  chlorides  of  these  radicals. 

3.  What  is  the  chief  chemical  characteristic  of  chromium  ?  and 
how  is  this  illustrated  by  reactions  [345]  to  [348]  ? 

4.  Can  you  form  any  theory  as  to  the  cause  of  the  difference  be- 
tween the  blue  and  green  modifications  of  the  chromic  salts  ?     Com- 
pare (337). 

5.  Blue  chromic  oxalate  is  made  by  boiling  a  solution  of  1 9  parts 
of  potassic  dichromate,  23  of  potassic  oxalate,  and  55  of  crystallized 
oxalic  acid.     The  red  salt  is  made  in  the  same  way  with  1 9  parts  of 
the  dichromate,  and  55  of  oxalic  acid  only.     Write  the  reactions. 

6.  What  inference  would  you  draw  from  the  peculiar  reactions  of 
chromic  chloride  ? 

7.  Explain  the  two  methods  of  making  potassic  dichromate,  and 
illustrate  the  process  by  reactions. 

8.  Represent  by  graphic  symbols  the  constitution  of  the  three  po- 
tassic chromates. 

9.  The  plumbic  chromates  may  all  be  represented  as  containing  the 
radical  (<9=P£»2),  including  the  very  rare   mineral  Phoenieochroite, 
which  contains  23.1  CrO3  and  76.9  PbO.    Write  the  symbols  of  the 
three  chromates  on  this  assumption,  and  weigh  their  probability  as 
compared  with  those  given  above.     Compare  the  reactions  of  the 
plumbic  with  those  of  the  potassic  salts,  and  consider  what  bearing 
the  general  isomorphism  of  the  chromates  with  the  sulphates  has  on 
the  question  (296). 

10.  Illustrate  by  reactions  the  method  of  dyeing  cloth  with  chrome 
orange. 

11.  Write  the  reaction  of  strong  hydrochloric  acid  on  potassic  di- 
chromate, assuming  that  the  principal  products  are  chromic  chloride 
and  chlorine  gas. 

12.  When  H^S  is  passed  through  a  solution  of  potassic  dichromate 
supersaturated  with  sulphuric  acid,  sulphur  is  precipitated,  and  the 
color  changes  from  red  to  green.     Write  the  reaction. 

13.  A  solution  of  potassic  dichromate  supersaturated  with  sul- 
phuric acid  is  much  used  instead  of  nitric  acid  in  the  porous  cup  of 


QUESTIONS  AND  PROBLEMS.  407 

Grove's  or  Bunsen's  voltaic  cell  (90).    What  is  the  theory  of  its 
action  ? 

14.  When  a  solution  of  potassic  dichromate  supersaturated  with 
sulphuric  acid  is  boiled  with  oxalic  acid,  all  the  chromic  acid  is  re- 
duced to  the  condition  of  a  chromic  salt,  and  an  equivalent  amount 
of  C02  is  set  free.     Write  the  reaction,  and  show  how  it  may  be  used 
to  determine  the  quantity  of  Cr09  in  the  dichromate. 

15.  The  chromium  in  a  soluble  chromate  may  also  be  estimated  as 
sesquioxide.     By  what  reactions  may  this  oxide  be  separated  in  a 
condition  to  be  accurately  weighed  ? 

16.  How  may  potassic  chromate  be  used  to  separate  barium  from 
calcium  and  strontium  ? 

17.  It  has  been  found  by  careful  experiment  that  10  grammes  of 
chromic  anhydride  yield  7.6048  grammes  of  chromic  oxide.     We 
know  also  the  Sp.  Gr.  of  chlorochromic  anhydride,  and  that  this  com- 
pound when  brought  in  contact  with  water  undergoes  the  change 
described  above.     Deduce  the  atomic  weight  of  chromium,  and  state 
the  steps  in  your  reasoning. 

18.  Write  the  reaction  by  which  chlorochromic  anhydride  is  ob- 
tained in  the  reaction  described  in  the  text.    It  may  also  be  made 
by  distilling  in  a  small  retort  a  dry  mixture  of  ferric  chloride  and 
chromic  oxide.     Write  the  reaction. 

19.  What  is  the  relation  of  the  compound  KCr03Cl  to  potassic 
chromate  on  the  one  side,  and  chlorochromic  anhydride  on  the 
other  ? 

20.  Write  the  reaction  by  which  CrF6  is  obtained  in  the  reaction 
described  above.     It  may  also  be  prepared  by  distilling  a  mixture  of 
potassic  dichromate,  ammonic  fluoride,  and  sulphuric  acid.     Write 
the  reaction. 

21.  Chromic  fluoride  is  decomposed  by  glass,  and  for  this  reason 
we  have  not  been  able  to  analyze  it,  or  to  determine  the  density  of 
its  vapor  satisfactorily.     Its  constitution  is  inferred  from  the  pro- 
ducts of  its  reaction  with  water.     Is  the  conclusion  trustworthy  ? 

22.  Write  the  reaction  of  ammonic  sulphide  on  a  solution  of 
chrome  alum. 


408  ALUMINUM.  [§352. 


Division  XHL 

352.  ALUMINUM.  Al  =  27 A.  —  Tetrad,  but  its  com- 
pounds all  contain  the  double  atom  [-4/2]  —  54.8,  which  is  a 
hexad  radical.  A  very  widely  distributed  element,  and,  after 
oxygen  and  silicon,  the  most  abundant  constituent  of  the  rocky 
crust  of  the  globe,  of  which  it  has  been  estimated  that  it  forms 
about  one  twelfth.  It  occurs  chiefly  in  combination  with  oxy- 
gen and  silicon,  and  most  of  the  siliceous  minerals,  and  rocks, 
when  not  pure  silica,  contain  aluminum  as  an  essential  ingredi- 
ent. For  a  full  enumeration  of  the  aluminum  minerals,  the  stu- 
dent must  consult  works  on  mineralogy.  The  following  list 
comprises  only  such  of  the  more  characteristic  native  compounds 
as  illustrate  the  chemical  relations  of  the  element. 


Fluorides. 

Cryolite  Orthorhombic  \_A12~]FQ  .  6NaF, 

Chiolite  Tetragonal  \_Alz~\FQ  .  3NaF, 

Pachnolite  Monoclinic  [J^JJJ  .  3[  Ga 

Thomsenolite  Monoclinic 


Oxides. 

Spinel  (Ruby)  Isometric 

Gahnite  Isometric 

Hercynite  Isometric  Fe^AQ  vm  04, 

Corundum,  Sapphire,  Oriental  Ruby,  Oriental  Topaz,  Oriental 

Amethyst,  &c.  Hexagonal 

Emery  Massive 


Hydrates. 

Gibbsite  Hexagonal 

Beauxite  Massive 

Diaspore  Orthorhombic 

Chrysoberyl  Orthorhombic  OAl    =  Of  G. 


§352.]  ALUMINUM.  409 

Sulphates. 

Alunogen  Monoclinic  [AQW$(S0^9.  1SH20, 

Aluminite  Massive  Of\_Al2]  =  02=(S02)  .  9#20, 

Paraluminite      Massive  05x[Al2~]2=02=(S02)  .  15ff20, 

Alum-stone  (Alunite) 

Rhombohedral   K^Al^^O^^SO^^H^  or 
\=SO«}  .  KfOrSO* .  Qff90. 


Octahedral  Alums. 

Potassium  Alum  Isometric       K2,[Al 

Ammonium  Alum        "       (NH^^Al^'&Otf^SO^t.  24J720. 

Fibrous  Alums. 
Pickeringite         Fibrous         Mg.[Al^\  vm 0^(80^^ .  22fT20, 


Apjolmite  Fibrous         Mn.\_Al^\  viii08vm(^02)4 .  22ff20, 

Halotrichite          Fibrous          Fe, [^/2]  vm  08vm (^02)4  .  2 2H2  0. 


Phosphates. 

Lazulite          Monoclinic  H^ Mg\_Al^\  x  010 : 

Turquois         Reniform  O^Al^lC 

Wavellite       Orthorhombic     \_Al2~\^'^Oi^'^(PO)^HQ .  5ff20. 


Silicates. 

Andalusite  Orthorhombic ) 

Cyanite  Monoclinic      ) 

Topaz  Orthorhombic 

Feldspars. 

Anorthite  Triclinic 

Labradorite  Triclinic 

Leucite  Isometric 

Oligoclase  Triclinic 

Albite  Triclinic 

Orthoclase  Monoclinic 
18 


410  ALUMINUM.  [§352. 

Clays. 
Kaolinite        Orthorhombic          H2,\_Al^  v^08^Si2  .  ff20, 


Halloysite       Massive  H^Al^  ™08™Si2  .  2ff20, 

Pyrophyllite  Orthorhombic          H^\_Alz~\  vm  O^Si3  02, 
Agalmatolite  Massive  H^Al^\  vm  O^Si^  04. 

Zeolites. 


Thomsonite  Orthorhombic  [Na^Oa 

Natrolite  Orthorhombic 

Scolecite  Monoclinic 

Analcime  Isometric  Na»\_  A12~]  via  08^Si4  04  .  2H2  0, 

Chabazite  Hexagonal  Ca[Al2~\  VM  08^Si4  04  .  6ff2  0, 

Harmotome  Orthorhombic  lJa[  4/f]  vm  0?MSiB  06  .  5R,  0, 

Heulandite  Monoclinic  Ca,[Al2~\  v»i  08™Si6  08  .  5ff2  0, 

Stilbite  Orthorhombic 


To  this  list  may  be  added  the  Garnets,  the  Scapolites,  the 
Epidotes,  the  Micas,  and  the  Chlorites,  all  large  and  important 
groups  of  minerals,  which  are  chiefly  silicates  of  aluminum,  but 
which  present  differences  of  composition  similar  to  those  illus- 
trated above.  It  is  impossible,  however,  in  the  present  state  of 
the  science,  to  deduce  from  the  results  of  the  analysis  of  many 
of  these  minerals  any  satisfactory  or  probable  rational  formula. 
The  mineral  Lapis  Lazuli  is  a  remarkable  illustration  of  this 
fact.  It  has  a  definite  crystalline  form  (Fig.  6),  and  has  long 
been  used  as  a  paint  under  the  name  of  ultramarine.  It  is  a 
silicate  of  aluminum,  calcium,  and  sodium,  with  a  sulphide  prob- 
ably of  iron  and  sodium  ;  but  numerous  analyses  have  given  no 
definite  clew  either  to  its  rational  formula  or  to  the  cause  of  its 
beautiful  blue  color.  Nevertheless,  the  pigment  is  now  made 
artificially  in  large  quantities,  by  combining  the  ingredients  in  the 
proportions  which  the  analyses  have  indicated,  and  this  would 
seem  to  show  that  it  is  the  theory  and  not  the  analysis  which  is 
at  fault.  This  subject  will  be  further  discussed  under  silicon. 

It  will  be  noticed  that  among  the  native  compounds  of  alumi- 
num are  included  several  of  the  precious  stones,  and  also  Emery, 
which  yields  an  exceedingly  hard  powder  very  much  used  in 
polishing.  From  the  clays  the  clay  slates,  and  to  a  less  extent 


§353.]  ALUMINUM.  411 

from  the  rarer  minerals  Alum-stone  and  Beauxite,  the  alums 
and  other  soluble  salts  of  aluminum  are  prepared.  Cryolite, 
now  imported  from  Greenland  in  large  quantities,  has  become 
an  important  source  of  soda-ash.  The  feldspars,  and  more  im- 
mediately the  clays  which  result  from  their  disintegration,  are 
largely  used  in  the  manufacture  of  porcelain  and  the  various 
kinds  of  earthenware.  The  coarser  clays  furnish  the  material 
for  bricks.  The  slates,  the  porphyries,  the  granites,  the  tra- 
chytes, the  green  stones,  the  lavas,  and  other  rocks,  rich  in 
aluminum,  are  used  in  building;  but  the  other  aluminous 
minerals,  with  few  exceptions,  find  no  important  applications 
in  the  arts. 

353.  Metallic  Aluminum.  —  Readily  obtained  by  reducing 
either  the  chloride  or  the  native  fluoride  (Cryolite)  with  metal- 
lic sodium.  It  has  a  brilliant  white  lustre,  and  possesses  to  a 
hio-h  degree  all  the  qualities  of  a  useful  metal.  It  has  a  low 

o  G  *• 

specific  gravity  (2.56),  but  still  a  very  great  tenacity.  It  is 
singularly  sonorous.  It  is  very  malleable  and  ductile.  It  is  an 
excellent  conductor  of  heat  and  electricity.  It  has  a  high  melting 
point,  although  somewhat  lower  than  that  of  silver.  It  does  not 
tarnish  in  the  air,  and  the  molten  metal  does  not  oxidize,  even 
when  heated  to  a  high  temperature.  Its  present  value,  which 
depends  solely  on  the  cost  of  extraction,  greatly  limits  the  ap- 
plications of  aluminum  in  the  arts ;  but,  nevertheless,  it  is  used 
to  a  limited  extent  for  cheap  jewelry,  and  in  a  few  philosophi- 
cal instruments,  where  it  is  important  to  combine  lightness  with 
strength.  An  alloy  of  copper  with  about  ten  per  cent  of  pure 
aluminum,  called  aluminum  bronze,  has  the  color  of  gold,  and 
an  almost  equal  power  of  resisting  atmospheric  agents. 

Neither  sulphuric  nor  nitric  acids,  when  cold  and  sufficiently 
diluted,  attack  aluminum,  and  nitric  acid  dissolves  it  only  slowly 
when  concentrated  and  boiling.  Hot  sulphuric  acid,  however, 
when  not  diluted  with  more  than  three  or  four  parts  of  water, 
dissolves  it  rapidly  with  the  evolution  of  hydrogen  gas.  The 
best  acid  solvent  is  hydrochloric  acid,  which  acts  on  the  metal 
at  the  ordinary  temperature  even  when  greatly  diluted ;  but, 
singularly,  the  metal  dissolves  almost  equally  well  in  a  solution 
of  caustic  soda  or  potash  ;  and  a  comparison  of  the  two  following 
reactions  will  make  evident  one  of  the  most  important  features 
in  the  chemical  relations  of  this  metal. 


412  ALUMINUM.  [§354 

qWlt,  +  Aq)  +  3IS-S!.  [350] 


AMI  +  (GNao-H  +  Aq  = 

-  Aq)  +  3HHH.  [351] 


354.  Compounds  in  which  [^44]  *'*  ^e  Basic  Radical.  —  The 
compounds  ot  this  class  are  isomorphous  with,  and  resemble  in 
almost  every  respect,  excepting  color,  the  corresponding  ferric 
salt.  Like  the  last,  they  have  a  great  tendency  to  form  basic 
salts,  and  they  exhibit  in  general  the  same  reactions  which  have 
been  already  described  (337).  The  use  of  the  soluble  aluminic 
salts  in  the  arts  depends,  —  1st.  Upon  their  tendency  to  form 
insoluble  basic  compounds,  and  2d.  Upon  the  fact  that  these 
basic  compounds,  including  the  hydrates,  eagerly  absorb  the 
soluble  organic  extracts  used  as  dyes.  When  organic  tissues, 
yarn  or  cloth,  are  dipped  into  a  solution  of  a  basic  aluminic  salt 
(compare  note  to  page  386),  or  when  in  the  process  of  calico- 
printing  a  similar  preparation  is  transferred  to  the  surface  of 
the  fabric  in  regular  designs,  the  insoluble  basic  compounds,  just 
referred  to,  are  formed  in  the  very  fibre  of  the  material,  and  be- 
come still  more  firmly  incorporated  when  the  tissue  is  exposed 
to  the  action  of  air,  steam,  or  other  agents  in  the  process  known 
as  ageing.  If  now  the  yarn  or  cloth  thus  prepared  is  dipped 
in  a  dye-  vat,  the  aluminic  compound  entangled  in  the  fibre  will 
seize  and  hold  the  coloring  matter,  and  hence  the  name  of  mor- 
dants, from  mordeo  (to  take  fast  hold  of},  applied  to  these  prep- 
arations of  aluminum.  The  basic,  ferric,  chromic,  and  stannic 
salts  act  in  a  similar  way,  and  are  also  used  as  mordants  ;  but 
while  the  colorless  aluminic  salts  take  the  true  color  of  the  dye, 
the  others  modify  the  tint  to  a  greater  or  less  extent.  Hence, 
in  the  process  of  calico-printing,  various  colors  are  obtained  from 
the  same  bath,  after  the  design  has  been  printed  on  the  cloth, 
with  the  appropriate  mordants.  When  salts  of  aluminum  are 
mixed  in  solution  with  dye-stuffs,  and  decomposed  by  an  alka- 
line reagent,  the  insoluble  hydrate  or  basic  salt  thus  formed 
carries  down  a  large  amount  of  the  coloring  matter,  and  these 
colored  precipitates,  when  dried,  are  used  as  pigments.  (Lakes.) 

Of  the  soluble  salts  of  aluminum,  which  may  be  used  as  mor- 
dants, the  most  important  are  the  alums,  whose  symbols  have 


J354.]  ALUMINUM.  413 

already  been  given  (352).  They  alone  crystallize  readily,  and 
can  therefore  be  easily  manufactured  on  a  large  scale  in  a  con- 
dition which  insures  purity.  The  alkaline  sulphate  which  they 
contain,  although  it  determines  the  peculiar  crystalline  charac- 
ter of  these  double  salts,  is  wholly  worthless  to  the  dyer,  and  it 
depends  chiefly  on  the  ruling  price  whether  the  ammonic  or  the 
potassic  salt  is  employed  in  their  manufacture.  Sodic  alum  does 
not  crystallize  readily,  and  is  therefore  never  used.  The  alu- 
minic  sulphate,  which  is  the  only  useful  part  of  the  alums,  is 
generally  obtained  by  decomposing  clay  or  shale,  after  it  has 
been  roasted  at  a  low  red  heat  with  sulphuric  acid.  It  is  made 
in  large  quantities  in  England  and  Germany  from  a  bituminous 
shale,  found  among  the  lowest  beds  of  the  coal  measures,  which 
contains  a  large  quantity  of  iron  pyrites  disseminated  through 
the  mass.  When  this  alum  schist,  or  alum  ore  as  it  is  called, 
is  slowly  burnt,  one  half  of  the  sulphur  of  the  pyrites  is  con- 
verted into  sulphuric  acid,  which  at  once  decomposes  a  portion 
of  the  aluminic  silicate  that  the  shale  contains,  thus  yielding  a 
certain  amount  of  aluminic  sulphate.  At  the  same  time  ferrous 
sulphate  is  formed  by  the  oxidation  of  the  residue  of  the  pyrites, 
and  when  the  roasted  mass  is  lixiviated  with  water  both  salts 
dissolve.  Lastly,  on  adding  to  the  solution,  after  concentration, 
potassic  or  ammonic  sulphate,  alum  is  formed,  which  is  sepa- 
rated from  the  ferrous  salt  by  crystallization. 

A  small  amount  of  potassium  alum  is  made  in  the  Roman 
States  from  Alum-stone  (352).  This  mineral,  when  roasted 
and  exposed  for  several  months  to  the  action  of  air  and  moist- 
ure, crumbles  into  a  sort  of  mud,  which,  when  lixiviated,  yields 
the  well-known  Roman  alum. 

Within  the  last  few  years  the  use  of  alum  has  been  in  a 
measure  superseded  by  the  introduction  into  commerce  of  pure 
aluminic  sulphate,  which  is  made  by  the  direct  action  of  sul- 
phuric acid  on  some  of  the  purer  varieties  of  clay,  and  freed 
from  iron  by  means  of  sodic  ferro-cyanide.  This  reagent  is 
added  to  the  solution  so  long  as  it  occasions  a  blue  precipitate, 
and  after  this  settles  the  clear  liquid  is  decanted  and  evapo- 
rated. The  residue  is  known  as  concentrated  alum.  The  salt 
may  be  crystallized  in  small  scales,  which  have  the  composition 
given  below. 

A  solution  of  basic  aluminic  acetate  is  also  much  used  as  a 


414  ALUMINUM.  [§355. 

mordant,  especially  for  madder  reds,  under  the  name  of  red 
liquor.  It  is  prepared  by  adding  plumbic  acetate  to  a  solution 
of  alum.  The  only  important  soluble  salts  of  aluminum,  which 
have  not  yet  been  mentioned,  are  the  chloride  and  nitrate. 


Aluminic  Chloride  [^]  1  C16  . 

Aluminic  Nitrate  [^4]i06I(A702)6  .  lSff20, 

Aluminic  Sulphate  [-44]  1  0^(S02)3  .  !Sff2  0. 

The  reactions  of  the  aluminic  salts,  when  in  solution,  differ 
from  those  of  the  corresponding  ferric  salts  chiefly  in  the  fact 
that  the  white  aluminic  hydrate,  which  is  precipitated  by  the 
alkaline  reagents,  dissolves  easily  and  perfectly  in  an  excess 
of  either  potassic  or  sodic  hydrate.  A  compound  of  aluminum 
may  generally  be  recognized  by  the  blue  color,  which  is  obtained 
when  the  solid,  previously  moistened  with  a  solution  of  cobaltic 
nitrate,  is  intensely  heated  in  the  oxidizing  flame  of  the  blow- 
pipe. 

355.  Compounds  in  which  \_Al<^\  is  the  Acid  Radical.  —  So- 
dic aluminate,  the  same  compound  which  is  formed  by  [351], 
is  now  manufactured  on  a  large  scale  from  Beauxite.  The  pul- 
verized mineral,  mixed  with  sodic  carbonate,  is  heated  to  bright 
redness,  and  the  soluble  aluminate  thus  formed  separated  from 
the  insoluble  residue  by  lixiviation  and  filtration.  On  evapo- 
rating the  clear  solution  (in  vacuo),  a  white  amorphous  solid  is 
obtained,  which  has  the  composition  already  given.  From  so- 
lutions of  this  compound  aluminic  hydrate  is  precipitated  on  the 
addition  of  any  soluble  acid,  or  even  on  exposure  to  the  carbonic 
acid  of  the  atmosphere,  and  this,  new  commercial  product  may 
be  used  with  great  advantage  as  a  substitute  for  alum.  A  re- 
markable reaction  occurs,  when  solutions  of  aluminic  chloride 
and  sodic  aluminate  are  mixed  together  in  atomic  proportions, 
illustrating  the  singular  twofold  relations  which  the  radical 
[-44]  may  sustain. 

Aq)  = 
+  (Wad  +  Aq).  [352] 

Although  other  aluminates  may  be  prepared,  the  salt  just 
described  is  the  only  noteworthy  example  of  this  class  of  com- 
pounds. Spinel,  however,  and  the  allied  minerals,  may  be 
regarded  as  meta-aluminates. 


358.]  QUESTIONS  AND  PROBLEMS.  415 


356.  Aluminic  Chloride,  [^4/2]lC76,  is  the  only  compound  of 
aluminum  with  chlorine.     It  is  made  by  passing  chlorine  gas 
into  a  mixture  of  aluminic  oxide  with  carbon,  heated  intensely 
in  an  earthen  retort,  when  the  chloride  distils   over  and  con- 
denses in  the  receiver  in  yellowish-white  crystalline  scales.     It 
is  a  fusible  solid,  which  volatilizes  at  a  temperature  only  a  few 
degrees  above  its  melting-point,  and  the  Sp.  Gr.  of  its  vapor 
confirms  the  theory  of  its  constitution  generally  accepted.     It 
eagerly  unites  with  water,  but,  like  ferric  chloride,  it  cannot  be 
recovered  by  evaporation  when  once  dissolved.    It  forms  double 
salts  with  the  alkaline  chlorides,  and  one  of  these,  \_AI^\ICIQ  . 
2Nad,  plays  an  important  part  in  the  preparation  of  aluminum. 

357.  Aluminic  Oxide,  A1203,  forms,  as  we  have  seen,  the 
mineral  Corundum.     It  may  be  obtained  artificially  by  igniting 
either  ammonia,  alum,  or  the  hydrate  obtained  indirectly  from 
Beauxite  (352).     It  is  a  hygroscopic  white  powder,  which  ad- 
heres to  the  tongue,  but  does  not  become  plastic  when  mixed 
with  water.     It  affects,  like  ferric  oxide,  two  conditions,  and  the 
change  from  one  to  the  other  is  accompanied  in  like  manner 
by  a  sudden  incandescence.     It  may  be  fused  by  the  compound 
blow-pipe,  and  the  resulting  transparent  bead,  like  corundum, 
has  a  hardness  only  inferior  to  that  of  diamond.     Moreover, 
colored  crystals,  resembling  the  ruby  and  the  sapphire,  have 
been  obtained  by  art 

358.  Aluminic  Sulphide,  [Al2~]=S&  is  formed  when  finely  di- 
vided aluminum  is  burnt  in  the  vapor  of  sulphur      It  is  a  black 
powder,  which  is  rapidly  decomposed  by  water  into  H^S  and 
[_A12~]  IO^HQ.     Hence  H%S  does  not  under  any  conditions  pre- 
cipitate aluminum  from  solutions  of  its  salts,  and  the  precipi- 
tate obtained  with  the  alkaline  sulphides  is  simply  the  normal 
hydrate. 

Questions  and  Problems. 

1.  Why  is  not  the  atomic  weight  of  aluminum  doubled  according 
to  the  principle  of  (19)  ? 

2.  Can  the  composition  of  the  native  fluorides  of  aluminum  be 
expressed  by  unitary  symbols  (69)  ?     Can  you  devise  a  process  by 
which  sodic  carbonate  may  be  made  from  Cryolite  ? 

3.  Compare  together  the  minerals  isomorphous  with  Spinel  (352), 


416  QUESTIONS  AND  PROBLEMS. 

(333),  (342),  and  show  in  what  two  ways  their  constitution  may  be 
expressed. 

4.  Compare  the  crystalline  form  and  hardness  of  corundum  with 
those  of  the  allied  sesquioxides. 

5.  Compare  the  native  aluminic  with  the  native  ferric  hydrates, 
and  show  how  many  of  the  possible  hydrates  are  represented  among 
the  native  aluminic  salts.     Use  the  table  of  ferric  hydrates  already 
made  (Prob.  68,  Div.  XL). 

6.  The  symbol  of  Chrysoberyl  may  be  written  after  the  type  of 
Spinel.    What  argument  may  be  urged  for  the  form  given  above? 

7.  Make  a  table  of  the  known  compounds  of  the  two  alum  types. 

8.  On  what  principle  are  the  aluminic  silicates  classified,  and  how 
do  the  several  members  of  each  group  differ  from  each  other  ? 

9.  Determine  the  atomic  ratios  between  the  various  radicals  in 
the  several  aluminic  salts,  sulphates,  phosphates,  and  silicates.     Con- 
sider, first,  the  simple  acid  radicals,  and  secondly,  the  compound  acid 
radicals  in  these  minerals. 

10.  What  inference  should  you  draw  from  a  comparison  of  the 
symbols  of  the  different  aluminum  compounds  as  regards  the  isomor- 
phism of  calcium  with  the  alkaline  radicals  ? 

11.  Some  varieties  of  Pyrophyllite  closely  resemble  Steatite.     By 
what  simple  blow-pipe  test  can  the  two  minerals  be  distinguished  ? 

12.  Write  the  reaction  of  sodium  on  sodio-aluminic  chloride  or 
fluoride,  and  calculate  how  much  aluminum  can  be  obtained  theo- 
retically for  every  kilogramme  of  sodium  employed. 

•  13.    How  does  the  Sp.  Gr.  of  aluminum  compare  with  that  of  the 
other  useful  metals  ? 

14.  Write  the  reaction  of  nitric  acid  and  that  of  sulphuric  acid  on 
aluminum,  assuming  that  nitric  oxide  is  evolved  in  the  first  case,  and 
hydrogen  gas  in  the  second. 

15.  Compare  reactions  [350]  and  [351],  and  point  out  the  differ- 
ent relations  of  the  radical  [Al^\  in  the  two  cases. 

16.  Explain  the  peculiar  relations  of  the  aluminic  salts  on  which 
their  use  as  mordants  depends. 

17.  Write  the  reaction  which  takes  place  when  sodic-carbonate  is 
added  to  a  solution  of  alum,  so  long  as  the  precipitate  first  formed  is 
redissolved,  assuming  that  in  the  basic  aluminic  sulphate,  which  re- 
mains in  solution,  the  atomic  ratio  between  the  basic  and  acid  radi- 
cals (S02)  is  as  3  : 1. 

18.  What  are  the  relative  intrinsic  values  of  potassium-alum,  am- 


QUESTIONS  AND  PROBLEMS.  417 

monium-alum,  and  crystallized  aluminic  sulphate,  taking  as  the  stand- 
ard the  quantity  of  normal  aluminic  hydrate  which  can  be  obtained 
from  each  ?  On  what  does  the  preference  given  to  the  alums  as 
mordants  chiefly  rest  ? 

19.  Explain  and  illustrate  by  reactions  the  process  of  manufactur- 
ing alum  from  the  alum  shales,  and  also  from  pure  clay. 

20.  Illustrate  by  reactions  the  change  of  Alum-stone  into  alum 
in  the  manufacture  of  Roman  alum. 

21.  If  a  portion  of  the  water  obtained  in  the  analyses  of  Aluminite 
and  Paraluminite  is  water  of  constitution,  how  may  the  symbols  be 
written  ? 

22.  Write  the  reaction  of  plumbic  acetate  on  a  solution  of  alum, 
assuming  that  in  the  basic  acetate,  which  remains  in  solution,  the 
atomic  ratio  is  3  : 1. 

23.  What  are  the  two  chief  differences  between  the  chemical  rela- 
tions of  iron  and  aluminum  ?     Illustrate  the  differences  by  reactions. 

24.  Explain  and  illustrate  by  reactions  the  method  of  manufactur- 
ing sodic  aluminate.     By  what  test  could  you  determine  when  all 
the  soda  has  been  converted  into  sodic  aluminate  ?    Why  evaporate 
solution  in  vacuof 

25.  Write  reaction  of  C02  on  solution  of  sodic  aluminate,  and  ex- 
plain the  use  of  this  salt  as  a  mordant. 

26.  Analyze  reaction  [352]. 

27.  Show  how  Spinel  could  be  derived  from  a  tetrahydro-magne- 
sic  aluminate. 

28.  Write  the  reaction  by  which  aluminic  chloride  is  formed,  and 
show  that  the  Sp.  Gr.  of  its  vapor  confirms  the  theory  of  its  consti- 
tution generally  accepted. 

29.  Write  the  reaction  which  takes  place  when  a  solution  of  alu- 
minic chloride  is  evaporated  to  dryness.     Consider  whether  the  pro- 
duet  formed  by  the  union  of  the  anhydrous  chloride  with  water  ought 
to  be  regarded  as  a  chemical  compound,  and,  if  so,  endeavor  to  rep- 
resent its  constitution  by  a  rational  symbol. 

30.  Compare  the  reactions  of  ammonic  sulphide  on  an  aluminic 
and  on  a  ferric  salt,  and  explain  the  cause  of  the  difference. 

31.  In  what  order  would  you  classify  the  several  radicals 
regarding  their  electro-negative  relations  ? 


18*  AA 


418  THE  PLATINUM  METALS.  [§359. 


Divisions  XIV.  to  XVI. 

359.  THE  PLATINUM  METALS.  —  The  six  metals 
which  follow  aluminum  in  our  classification  (Table  II.)  are  al- 
ways found  in  the  native  state,  although  more  or  less  alloyed 
with  each  other.  "  Platinum  Ore  "  is  found  in  several  coun- 
tries, but  at  least  nine  tenths  of  the  commercial  supply  comes 
from  the  Ural.  It  is  everywhere  obtained  by  washing  alluvial 
material,  generally  in  small  rounded  metallic  grains,  although 
masses  of  considerable  size  are  occasionally  found.  The  follow- 
ing analyses  by  Deville  and  Debray  will  give  an  idea  of  its 
composition  :  — 


Choco 

Pt 
86.20 

Au 
1.00 

Fe 
7.80 

Ir 
0.85 

Rh 
1.40 

Pd 
0.50 

Ou 
0.60 

Ir-Os 
0.95 

Sand 
0.95 

California 

85.50 

0.80 

6.75 

1.05 

1.00 

0.60 

1.40 

1.10 

2.95 

Oregon 
Australia 

51.45 
61.40 

0.85 
1.20 

4.30 
4.55 

0.40 
1.10 

0.65 
1.85 

0.15 
1.80 

2.15 
1.10 

37.30 
26.00 

3.00 
1.20 

Eussia  76.40     0.40     11.70     4.30     0.30     1.40     4.10       0.50     1.40 

In  this  ore  the  grains  of  "Native  Platinum,"  which  have  a  steel- 
gray  color,  are  always  more  or  less  mixed  with  those  of  a  dis- 
tinct mineral  species  called  "  Iridosmine,"  l  which  have  usually 
a  lighter  color,  and  consist  chiefly  of  iridium  and  osmium,  al- 
loyed with  small  quantities  of  rhodium  and  ruthenium.  Hence 
from  the  above  analyses  the  amounts  of  iridosmine  (Ir-  Os)  and 
sand  must  be  subtracted  in  order  to  obtain  the  composition  of 
native  platinum  proper. 

In  the  old  method  of  manufacturing  platinum,  the  ore  is 
treated  with  aqua-regia,  which  dissolves  the  platinum  and  the 
metals  directly  alloyed  with  it,  but  does  not  affect  the  iridos- 
mine, the  titaniferous  iron,  and  other  resisting  minerals,  which 
are  frequently  mixed  with  the  "Native  Platinum."  To  the  so- 
lution thus  obtained,  when  brought  into  suitable  condition,  am- 
monic  chloride  is  added,  which  precipitates  all  the  platinum 
[176]  as  ammonio-platinic  chloride.  This  precipitate,  when 
ignited,  leaves  the  metal  in  a  pulverulent  condition  (platinum 

1  Iridosmine  is  frequently  associated  with  California  gold,  and  is  separated 
from  it  at  the  Assay  Offices  in  considerable  quantities.  Being  heavier  than 
gold  it  sinks  to  the  bottom  of  the  crucible  when  the  metal  is  fused. 


§360.]  RUTHENIUM.  419 

sponge),  which  is  welded  into  a  compact  mass  by  heat  and 
pressure. 

In  the  new  method  of  Deville  and  Debray  the  platinum  is 
first  united  to  metallic  lead,  which,  as  it  does  not  alloy  with  iri- 
dosmine,  separates  the  platinum  from  the  chief  impurities  in  the 
ore.  The  lead  is  subsequently  removed  by  cupellation,  and  the 
crude  platinum  purified  by  melting  it  in  a  crucible  of  lime  with 
a  powerful  oxy hydrogen  flame.  Indeed,  an  alloy  of  platinum 
with  a  small  amount  of  iridium  and  rhodium,  well  adapted  for 
chemical  vessels,  may  be  obtained  directly  from  the  ore  by  fus- 
ing it  with  the  same  flame  on  a  bed  of  lime,  using  a  small 
amount  of  lime  as  a  flux.  The  palladium  and  osmium  present 
are  thus  volatilized,  while  the  copper  and  iron  form  fusible  com- 
pounds with  the  lime. 

From  the  "  platinum  residues,"  as  they  are  termed,  the  asso- 
ciated metals  can  only  be  separated  by  refined  analytical  meth- 
ods, and  our  knowledge  of  the  chemical  relations  of  these  rare 
elements  is  still  very  imperfect.  Necessarily,  therefore,  they 
must  occupy  a  very  subordinate  place  in  an  elementary  treatise, 
and  they  are  here,  as  elsewhere,  classed  together,  more  in  con- 
sequence of  their  intimate  association  in  nature  and  resemblances 
as  metals,  than  from  any  well-defined  chemical  relationship. 

360.  RUTHENIUM  (Ru  =  104.4)  is  a  white  metal,  very 
hai  and  brittle,  with  difficulty  fusible  before  the  oxy  hydrogen 
blow-pipe.  Sp.  Gr.  when  fused  11  to  11.4.  It  is  scarcely  at- 
tacked by  nitro-muriatic  acid,  but  it  is  easily  oxidized  when 
fused  with  potassic  hydrate  (especially  if  a  little  nitre  be  added), 
yielding  potassie  rutheniate,  which  forms  with  water  an  orange- 
colored  solution.  The  pulverized  metal  heated  in  a  current  of 
air  rapidly  absorbs  oxygen,  and  the  oxides  cannot  be  reduced 
by  heat  alone. 

Five  oxides  are  known,  —  First,  Ru  0,  which  has  a  dark- 
gray  color  and  metallic  lustre.  It  is  not  acted  on  by  acids,  but 
is  reduced  by  hydrogen  at  the  ordinary  temperature.  Secondly, 
Ru20s  ,which  is  the  product  when  the  metal  is  oxidized  by  the 
air.  It  has  a  deep-blue  color,  is  also  insoluble  in  acids,  and  is 
reduced  by  hydrogen,  but  only  at  a  higher  temperature.  The 
corresponding  hydrate,  [j??w2]l//06,  which  dissolves  with  yellow 
color  in  acids,  but  is  insoluble  in  water  or  alkalies,  is  also  known. 
Thirdly,  Ru  02,  which  is  a  dark,  greenish-blue  powder,  and  the 


420  OSMIUM.  [§361. 

hydrate  Ru^Ho^  which  dissolves  both  in  acids  and  alkalies. 
Fourthly,  Ru  03,  which  is  the  assumed  anhydride  of  the  yellow 
rutheniate,  formed  when  the  metal  is  ignited  with  a  mixture  of 
potassic  hydrate  with  potassic  nitrate  or  chlorate.  This  char- 
acteristic compound  is  decomposed,  like  potassic  manganate,  by 
acids  and  even  by  organic  substances.  Lastly,  Ru  04,  which  is 
a  very  volatile  golden-yellow  crystalline  solid,  melting  at  58° 
and  boiling  at  about  100°. 

Ruthenium  forms  three  chlorides :  Ru  Cl%,  which  is  known  both 
as  an  insoluble  black  crystalline  powder  and  as  forming  a  fine 
blue  solution  ;  [/?w2]  CIQ,  which  forms  yellow  solutions  and  solu- 
ble compounds  with  the  alkaline  chlorides,  as  \_Ru^\  C16 .  kKCl; 
lastly,  RuCli,  known  only  in  its  double  salts,  JKuCl4  .  2KCI 
and  RuCl±.  2(Nff4)  Cl,  which,  like  the  corresponding  platinum 
salt,  crystallizes  in  octahedrons  (366),  but  appears  to  be  dismor- 
phous,  as  it  forms  under  certain  conditions  hexagonal  prisms. 

When  ff2S  is  passed  through  a  solution  of  the  yellow  chlo- 
ride, it  partly  precipitates  the  ruthenium  as  a  sulphide,  but  at 
the  same  time  it  partially  reduces  \_Ru^\ClQ  to  RuCl2,  which 
gives  to  the  supernatant  liquid  a  fine"  azure-blue  color.  Zinc 
effects  the  same  reduction,  and  this  reaction  is  very  delicate  and 
characteristic. 

361.  OSMIUM  ( Os  =  1 99.2).  —  In  the  most  compact  con- 
dition in  which  this  metal  has  been  obtained,  it  has  Sp.  Gr.  = 
21.4,  and  a  bluish  tinge  of  color  resembling  that  of  zinc.  It 
has  never  been  fused,  but  it  slowly  volatilizes  at  the  tempera- 
ture at  which  ruthenium  and  iridium  melt.  When  finely  di- 
vided, it  is  oxidized  by  nitric  acid,  but  in  its  more  compact  state 
it  resists  even  aqua-regia.  When  heated  in  a  current  of  air,  it 
oxidizes  much  more  readily  than  ruthenium,  passing  at  once  to 
the  highest  degree  of  oxidation,  OsO^  and  forming  a  volatile 
compound  resembling  Ru  04.  Indeed,  when  in  powder,  osmium 
is  very  combustible,  and  even  when  compact  it  takes  fire  at  a 
temperature  scarcely  exceeding  the  melting-point  of  zinc,  and 
its  strong  tendency  to  form  this  volatile  oxide  is  the  most  striking 
character  of  the  element.  Its  oxides  and  chlorides  correspond 
almost  precisely  both  in  composition  and  chemical  relations  to 
those  of  ruthenium.  The  three  lower  oxides  all  form  hydrates, 
but  have  no  well-marked  basic  character.  Osmic  anhydride, 
Os03,  is  unknown,  but  potassic  osmate,  K2=  02=  Os  02 .  2Jf2  0, 


§362.]  RHODIUM.  421 

can  easily  be  obtained  in  large  rose-colored  octahedrons.  The 
volatile  oxide,  Os  04,  just  referred  to,  forms  colorless  acicular 
crystals,  which  are  very  fusible  and  freely  soluble  in  water.  It 
boils  at  about  100°,  emitting  an  extremely  irritating  and  delete- 
rious vapor,  whose  pungent  odor,  resembling  that  of  chlorine,  is 
very  characteristic.  When  pulverized  osmium  is  heated  in  per- 
fectly dry  chlorine  gas,  there  is  first  formed  a  blue-black  subli- 
mate of  Os  Gift  and  afterwards  a  red  sublimate  of  Os  C14.  Os- 
mious  chloride  gives  a  dark  violet-blue  solution,  while  osmic 
chloride  gives  a  yellow  solution ;  and  when  exposed  to  the  air, 
the  first  rapidly  changes  to  the  last.  By  the  action  of  reducing 
agents  the  change  may  be  reversed.  All  the  chlorides  of  osmium 
form  double  salts  with  the  alkaline  chlorides.  The  most  inter- 
esting are  the  compounds  corresponding  to  potassio-platinic  chlo- 
ride, Os  C14  .  2KGI,  which  forms  beautiful  red  octahedral  crys- 
tals, sparingly  soluble  in  water,  and  [  0s2]  #4  •  &KGI .  Qff2  0, 
which  resembles  a  characteristic  Rhodium  compound  mentioned 
below. 

362.  RHODIUM  (Rh  =  104.4)  is  a  very  hard  grayish- 
white  metal,  barely  fusible  in  an  oxyhydrogen  flame.  Sp.  Gr. 
after  fusion  12.1.  It  is  imperfectly  malleable,  but  when  alloyed 
with  platinum  may  be  easily  worked.  The  pure  metal  is  insol- 
uble in  acids,  although  when  alloyed,  in  not  too  large  quantity, 
with  platinum,  copper,  bismuth,  or  lead,  it  dissolves  with  them 
in  aqua-regia.  Although  unalterable  in  the  air,  rhodium  com- 
bines both  with  oxygen  and  chlorine  at  a  red  heat.  It  is  read- 
ily oxidized  by  fusion  with  nitre  or  peroxide  of  barium.  Fused 
with  potassic  bisulphate,  it  is  converted  into  soluble  rhodio-po- 
tassic  sulphate,  and  when  heated  with  sodic  or  basic  chlorides 
in  a  current  of  chlorine  gas,  it  yields  various  double  salts,  which 
are  likewise  easily  soluble. 

Although  several  oxides  of  rhodium  have  been  distinguished, 
the  only  one  which  as  yet  has  been  well  defined  is  Rh%  03,  Rho- 
dic  Oxide,  and  this  compound  evidently  marks  the  prevailing 
quantivalence  of  the  element.  In  this  condition  rhodium,  un- 
like the  elements  with  which  it  is  associated,  appears  to  be  a 
well-marked  basic  radical,  forming  stable  salts  with  several  of 
the  acids.  Thus  we  have 

Rhodic  Hydrate  [#A2]  1 0&H& 

Rhodic  Acetate  [JftJ 1 06i (CZH^O\  .  5ffzO, 


422  IRIDIUM.  [§363 


Khodic  Nitrate  [J&  J  1  0^(N02\  .  4  J72  O, 

Rhodic  Sulphite  [J»y  1  0<M(SO)3  .  QH20, 

Ehodic  Sulphate  P*J  1  06!(S<92)3  .  12H2  0, 

Potassio-rhodic  Sulphate  K6,[JRh2~]™Ol2™(S02)G. 

In  like  manner  the  only  well-defined  compound  of  rhodium 
and  chlorine  is  [7?A2]1C76,  a  brownish-red,  indifferent  body,  in- 
soluble in  all  acids  and  alkalies.  A  solution  of  the  chloride  may 
be  obtained  by  dissolving  R2  03  in  hydrochloric  acid,  and  from 
this  several  well-crystallized  soluble  double  chlorides  may  be 
prepared,  as 


Potassio-rhodic  Chloride  [JftJ  016  .  QKOl  .  6ff20, 

Sodio-rhodic  Chloride  [JW  J  Ol&  .  QNa  Cl  .  24/4  0. 

They  all  have  a  ruby  or  rose  color,  whence  the  metal  takes  its 
name,  from  p68ov,  a  rose. 

363.  IRIDIUM  (/r  =  196)is  a  very  hard,  white,  brittle 
metal.  Though  even  less  fusible  than  rhodium,  it  has  been 
melted  on  lime  with  the  oxyhydrogen  flame  and  by  the  voltaic 
arc.  Sp.  Gr.  after  fusion  21.15.  The  pure  metal  is  not  acted 
on  by  any  acid,  but  when  alloyed  with  platinum  it  dissolves  in 
aqua-regia.  It  may  also  be  rendered  soluble  by  fusion  with  al- 
kaline reagents,  under  the  same  conditions  as  rhodium.  Unless 
in  very  fine  powder  it  does  not  oxidize  when  heated  in  the  air. 
It  forms  two  principal  oxides,  Ir2  Os  and  7r<92,  and  the  corre- 
sponding hydrates  are  readily  obtained.  The  hydrates  dissolve 
in  acids,  but  do  not  form  definite  oxygen  salts  unless  associated 
with  other  basic  radicals.  There  are  also  chlorides  corresponding 
to  the  oxides,  which  form  crystalline  double  salts  with  the  alka- 
line chlorides,  closely  resembling  the  similar  compounds  already 
described.  Thus  we  have 


Potassio-iridous  Chloride         [7rJ  C76  .  §KCl  .  6ff2O, 
Sodio-iridous  Chloride  [7rJ  CIQ  .  6Na  01  . 


which  contain  the  radical  [/rjl,  and  also 

Potassio-iridic  Chloride  Ir0l4  .  2KCI, 

Sodio-iridic  Chloride  IrOl4  .  ZNaCl  .  6ff2O, 

which  contain  the  radical  fe,  the  last  class  being  less  soluble 


§364.]  PALLADIUM.  423 

than  the  first.  Most  of  the  compounds  of  iridium  have  a  strong 
coloring  power,  those  containing  the  radical  [/rjl  giving  in  gen- 
eral green,  and  those  containing  the  radical  Ir=  red  solutions. 
The  iridic  compounds  are  the  most  stable,  but  under  the  action 
of  reducing  or  oxidizing  agents  one  condition  of  the  element 
readily  passes  into  the  other,  and  the  changes  of  color  which 
then  take  place,  giving  under  different  conditions  beautiful 
shades  of  purple,  violet,  and  blue,  are  very  striking  and  char- 
acteristic. Hence  the  name  Iridium,  from  iris,  the  rainbow. 
Under  certain  circumstances  this  element  appears  to  manifest 
still  other  degrees  of  quantivalence,  and  compounds  containing 
both  Ir=  and  Ii\  have  been  distinguished,  the  last  acting  as  an 
acid  radical  in  the  product  obtained  by  fusing  iridium  with  nitre, 
which  gives,  with  water,  a  deep  blue  solution,  and  is  supposed  to 
contain  the  compound  K2=0^1r02\  but  our  knowledge  on  this 
subject  is  still  very  imperfect. 

364.  PALLADIUM  (Pd  =  106.6).  Sp.  Gr.  =  11.4.— 
This  brilliant  white  metal  resembles  platinum  more  closely  than 
either  of  its  associates.  Although  best  known  as  a  subordinate 
constituent  of  platinum  ore,  it  has  also  been  found  (in  Brazil) 
native,  in  masses  of  considerable  size.  It  is  harder  than  plat- 
inum, has  less  tenacity,  and  is  not  so  ductile;  but,  nevertheless, 
it  can  be  wrought  with  facility.  It  cannot  be  fused  in  an  ordi- 
nary wind-furnace,  but  before  the  compound  blow-pipe  it  melts 
more  readily  than  platinum,  and  if  heated  on  lime  is  slowly 
volatilized,  giving  off  a  green  vapor.  Like  the  noble  inetals, 
its  oxides  and  chlorides  are  reduced  by  heat  alone.  Yet 
when  exposed  to  the  air  at  a  low  red  heat  its  surface  be- 
comes covered  with  an  iridescent  film  of  oxide,  which  is  dis- 
persed, however,  at  a  higher  temperature.  Palladium  is  acted 
on  by  chemical  agents  more  readily  than  platinum.  Though 
only  slightly  attacked  by  pure  hydrochloric  or  sulphuric  acids,, 
it  dissolves  readily  in  nitric  acid,  and  also  in  aqua-regia,  or  in 
sulphuric  acid  when  mixed  with  a  small  amount  of  nitric  acid. 
It  is  also  rendered  soluble  by  fusion  with  alkaline  reagents,  un- 
der the  same  conditions  as  the  preceding  metals. 

Palladium  differs  from  the  associated  elements  very  markedly 
in  that  it  affects  most  readily  the  condition  of  a  bivalent  positive 
radical.  Thus  we  easily  obtain,  by  dissolving  the  metal  in  the 
respective  acids,  the  two  following  crystalline,  salts :.— - 


424  PALLADIUM.  [§364. 


Palladious  Nitrate     (Brown)  Pd= 

Palladious  Sulphate        "  Pd=0./S02  .  2H20. 

The  corresponding  hydrate  is  precipitated  by  sodic  carbonate 
from  solutions  of  either  of  these  salts  as  a  dark  brown  powder. 
The  oxide  PdO,  a  black  powder,  is  obtained  by  heating  the  ni- 
trate to  dull  redness.  The  chloride  PdCl2  forms  brown  hydrous 
crystals,  when  a  solution  of  the  metal  in  aqua-regia  is  evapo- 
rated to  dryness,  and  by  uniting  with  other  chlorides  yields 
definite  crystalline  salts,  as,  for  example,  PdCl2  .  2KCI,  which 
is  easily  obtained  in  dull  yellow  prismatic  crystals. 

Palladium  also  forms  another  class  of  compounds  in  which 
its  atoms  are  quadrivalent;  but  these  are  all  very  unstable. 
The  chloride  Pd  C14  has  never  been  isolated,  but  the  compound 
PdCli  .  2KCI,  which  has  been  obtained  in  red  octahedral  crys- 
tals, attests  the  relationship  of  this  element  to  those  with  which 
it  is  classed. 

But  of  all  the  characteristics  of  palladium  the  most  notewor- 
thy is  the  power  which  the  metal  possesses  of  absorbing  hydro- 
gen gas.  It  appears  from  the  recent  experiments  of  Professor 
Graham  that,  in  the  condition  in  which  it  is  deposited  by  elec- 
trolysis, this  metal  will  absorb  or  "  occlude  "  nearly  1,000  times 
its  volume  of  hydrogen,  which  amounts  to  about  three  fourths 
of  one  per  cent  of  its  weight,  and  in  other  conditions  of  the 
metal  the  power  of  absorption  is  very  great,  although  not  so 
large.  The  same  phenomenon  to  a  less  degree  has  also  been 
observed  with  platinum  and  iron,  and  considerable  amounts  of 
"  occluded  "  hydrogen  have  been  discovered  in  some  of  the  me- 
teors. The  gas  thus  taken  up  by  these  metals  is  not  simply 
mechanically  condensed,  as  when  absorbed  by  charcoal,  but  ap- 
pears to  be  in  a  state  of  partial  chemical  combination  like  that 
of  a  solution  or  an  alloy  ;  for  we  find  that,  while  the  hydrogen 
is  easily  expelled  by  heat,  it  shows  no  tendency  to  escape  into 
a  vacuum.  The  gas,  however,  readily  passes  through  a  heated 
palladium  or  platinum  plate  by  an  action  similar  to  dialysis  (57), 
and  these  metals  seem  to  partake  more  or  less  of  a  colloidal 
condition.  By  a  similar  action  carbonic  oxide  passes  through 
•  the  iron  walls  of  furnaces,  and  this  class  of  phenomena,  when 
further  investigated,  will  undoubtedly  be  found  to  be  quite 
general. 


§366.]  PLATINUM.  425 

When  a  mass  of  palladium,  charged  as  above  described,  is 
exposed  to  the  air,  it  sometimes  becomes  suddenly  heated  from 
the  oxidation  of  the  hydrogen  it  contains,  and  the  well-known 
power  of  platinum,  especially  when  finely  divided,  as  in  the 
condition  of  sponge  or  the  so-called  platinum  black,  to  determine 
the  union  of  hydrogen  and  oxygen,  and  even  to  ignite  a  hydro- 
gen jet,  together  with  a  large  class  of  similar  effects,  may  be 
explained  on  the  same  principle. 

365.  Hydrogenium.  —  The  quantity  of  hydrogen  "  occluded" 
by  palladium  amounts  to  nearly  one  equivalent  for  each  equiv- 
alent of  the  metal,  and  produces  a  marked  change  in  its  physical 
qualities.     The  volume  of  the  metal  is  increased,  its  tenacity 
and  conducting  power  for  electricity  diminished,  and  it  acquires 
a  slight  susceptibility  to  magnetism,  which  the  pure  metal  does 
not  possess.     From  these  facts  Professor  Graham  infers  that 
the  metal  charged  with  gas  is  an  alloy  of  palladium  and  metallic 
hydrogen,  which  he  prefers  to  call  hydrogenium,  and  it  would 
appear  that  in  this  remarkable  product  the  anticipations  of 
chemists  in  regard  to  the  metallic  condition  of  hydrogen  have 
been  realized.     If  this  inference  is  correct,  and  if,  as  is  gener- 
ally the  case,  the  volume  of  the  alloy  is  equal  to  the  sum  of  the 
volumes  of  the  two  metals,  then  the  Sp.  Gr.  of  hydrogenium 
(deduced  from  that  of  the  alloy)  must  be  about  2.     The  chem- 
ical qualities  of  this  alloy  are  very  remarkable.     It  precipitates 
mercury  from  a  solution  of  its  chloride,  and  in  general  acts  as  a 
strong  reducing  agent.     Exposed  to  the  action  of  chlorine,  bro- 
mine, or  iodine,  the  hydrogen  leaves  the  palladium  and  enters 
into  direct  union  with  these  elements.     Moreover,  from  a  pal- 
ladium wire  charged  with  the  gas,  and  covered  with  calcined 
magnesia  (to  render  the  flame  luminous),  the  hydrogen  burns, 
when  lighted  by  a  lamp,  like  oil  from  a  wick.     So  far,  there- 
fore, as  its  chemical  activities  are  concerned,  hydrogenium  bears 
somewhat  the  same  relation  to  hydrogen  gas  that  ozone  bears 
to  ordinary  oxygen.     Palladium  plate  or  wire  is  most  readily 
charged  with  hydrogen  by  making  it  the  negative  pole  of  a  gal- 
vanic battery  in  the  process  of  electrolyzing  water.     (Fig.  84.) 

366.  PLATINUM.   Pt  =  197.4.    Sp.  Gr.  =  21.5.  —  The 
extended  use  of  this  metal  in  practical  chemistry  has  made  its 
appearance  familiar  to  every  student  of  the  science.     Platinum 
utensils  have  been  of  inestimable  value  in  chemical  investiga- 


426  PLATINUM.  [§366. 

tions,  on  account  of  the  infusibility  of  the  metal,  and  its  won- 
derful power  of  resisting  chemical  agents.  It  not  only  does  not 
oxidize  when  heated  in  the  air,  but  none  of  the  acids  singly  act 
upon  it,  and  even  aqua-regia  dissolves  it  but  slowly.  The  metal 
is  corroded  when  heated  to  redness  in  contact  with  the  caustic 
alkalies  or  alkaline  earths,  especially  the  hydrates  of  lithium  or 
barium,  but  the  alkaline  chlorides,  carbonates,  or  sulphates  may 
be  fused  in  platinum  crucibles  without  injuring  them.  Dry  chlo- 
rine has  no  action  on  the  metal  at  any  temperature,  and  both  the 
oxides  and  the  chlorides  are  reduced  by  heat  alone.  Platinum, 
however,  readily  alloys  with  several  of  the  other  metals,  and  care 
must  be  taken  to  conduct  no  operations  in  platinum  vessels  by 
which  a  fusible  metal  may  be  reduced.  Phosphorus  and  sulphur 
also  act  on  platinum  to  a  limited  extent. 

Platinum  is  very  ductile  and  malleable,  and  two  pieces  of  the 
metal  may  be  welded  together  at  a  white  heat,  although  to  melt 
it  the  temperature  of  the  oxyhydrogen  flame  is  required. 
Melted  platinum  absorbs  oxygen  from  the  air,  and,  like  silver 
(140),  spits  if  suddenly  cooled.  The  same  phenomenon  has 
been  observed  with  palladium  and  rhodium. 

Platinum  affects  the  condition  both  of  a  bivalent  and  a  quad- 
rivalent radical,  but  its  affinities  are  at  best  very  feeble.  When 
dissolved  in  aqua-regia  the  product  first  formed  is  probably 
PtCl4  .  %HCl,  and  from  this  solution  a  large  number  of  other 
compounds  of  the  same  type  are  easily  obtained,  and  these  are 
the  most  important  compounds  of  this  element.  We  have,  for 
example, 


Bario-platinic  Chloride  PtCl4 

Magnesio-platinic  Chloride  PtCl4  .  MgCl2.  6H20, 

Sodio-platinic  Chloride  Pt  C14  .2NaCl.GH20, 

Potassio-platinic  Chloride  PtCl4  .  2KCI, 

Ammonio-platinic  Chloride  Pt  C14 


These  salts  have  all  a  characteristic  yellow  color  except  in  the 
few  cases  where  the  second  basic  radical,  having  itself  a  strong 
coloring  power,  modifies  the  result.  The  barium  and  sodium 
salts  crystallize  in  prisms.  The  magnesium  salt,  and  the  cor- 
responding compounds  of  cadmium,  zinc,  copper,  cobalt,  and 
manganese,  which  are  isomorphous  with  it,  crystallize  in  rhom- 


§367.]  PLATINUM.  427 

bohedrons.  The  potassium  and  ammonium  salts  crystallize  in 
regular  octahedrons.  The  hydrous  salts  are  all  soluble  in  water, 
but  the  last  two  are  nearly  insoluble  in  water,  and  wholly  insol- 
uble in  alcohol.  They,  therefore,  can  easily  be  obtained  by  pre- 
cipitation, and  on  this  fact  are  based  several  important  methods 
of  quantitative  analysis.  Moreover,  compounds  of  the  same 
general  type  may  be  formed  with  almost  all  the  organic  bases 
and  vegetable  alkaloids,  and  they  furnish  one  of  the  simplest 
means  of  determining  the  molecular  weight  of  such  substances 
(68). 

If  the  solution  of  ^platinum  in  aqua-regia  is  evaporated  over 
a  water-bath,  the  amorphous  brownish-red  residue  (soluble  both 
in  water  and  alcohol)  may  be  regarded  as  PtCl± ;  but  if  the  tem- 
perature is  raised  to  200°  one  half  of  the  chlorine  escapes,  and 
the  insoluble  greenish-brown  solid  then  obtained  is  Pt  C72.  Plat- 
inous  chloride  is  not  acted  on  even  by  nitric  or  sulphuric  acids, 
but,  out  of  contact  with  the  air,  it  dissolves  unchanged  in  hydro- 
chloric acid,  although  platinic  chloride  is  formed  if  air  has  access 
to  the  solution.  It  also  combines  with  other  metallic  chlorides, 
forming  a  large  number  of  crystalline  salts,  as,  for  example, 

Ammonio-platinous  Chloride  PtCl2 .  2(NH4)  Cl, 

Potassio-platinous  Chloride  PtCl2 .  ZKCl, 

Argento-platinous  Chloride  PtCl2 .  2AgCl, 

Zinco-platinous  Chloride  Pt  C12 .  Zn  C12, 

Bario-platinous  Chloride  PtCl2 .  BaCl2 .  3ff20. 

These  salts  are  all  readily  prepared  from  the  hydrochloric  acid 
solution  (PtCl2 .  2HCI  +  ^-q)>  an(i  are  generally  distinguished 
by  a  red  color. 

367.  Platinous  Hydrates,  Pt=Ho2,  which  is  obtained  as  a  black 
powder  by  digesting  platinous  chloride  with  a  solution  of  caustic 
potash,  dissolves  both  in  alkalies  and  acids,  but  the  compounds 
thus  formed  are  very  unstable.  Platinous  nitrite  and  sulphite, 
however,  form  crystallizable  double  salts  with  several  of  the 
more  basic  radicals.  Platinic  Hydrate,  Pt^Ho^  prepared  indi- 
rectly from  platinic  chloride,  is  also  soluble  both  in  acids  and 
alkalies.  The  compounds  thus  formed  are  all  unstable,  those 
in  which  the  element  acts  as  an  acid  radical  being  the  more 
definite.  Platinic  sulphate  and  platinic  nitrate,  although  they 


428  QUESTIONS  AND  PKOBLEMS.  [§367 

have  not  been  crystallized,  are  easily  obtained  in  solution,  the 
sulphate  by  evaporating  a  solution  of  the  chloride  with  sul- 
phuric acid,  the  nitrate  by  decomposing  the  sulphate  with  baric 
nitrate.  Lastly,  by  cautiously  heating  the  hydrates  we  can 
obtain  the  corresponding  oxides,  but  if  the  temperature  exceeds 
a  limited  degree  they  are  at  once  completely  reduced. 

By  acting  on  different  platinum  salts  with  ammonia,  a  re- 
markable class  of  compounds  have  been  obtained,  which  are 
best  regarded  as  salts  of  platinum  bases,  and  as  formed  by  the 
coalescing  of  two  or  more  molecules  of  H$N  soldered  together 
by  atoms  of  Pt=  or  Pfc,  although  they  probably  contain  in  some 
cases  more  complex  platinum  radicals.  Similar  compounds  have 
also  been  formed  with  palladium  and  iridium;  but,  although 
highly  interesting  subjects  of  study  on  account  of  their  manifold 
types  and  complex  constitution,  this  new  class  of  ammonia  bases 
illustrate  no  principles  not  already  fully  discussed,  and  for  a 
description  of  them  we  must  refer  to  more  extended  works. 


Questions  and  Problems. 

1.  Calculate  the  percentage  composition  of  platinum  ore,  elimi- 
nating from  the  results  given  in  (359)  the  quantity  of  iridosmine  and 
sand  with  which  the  ore  is  mixed. 

2.  Explain  the  old  method  of  working  platinum  ores,  and  illustrate 
the  various  steps  in  the  process  by  reactions.     To  what  extent  are 
the  associated  metals  precipitated  by  ammonic  chloride  ? 

3.  Point  out  the  relationship  between  the  platinum  metals  and 
iron.     Compare  also  these  elements  with  each  other,  and  consider 
especially  the  characteristics  distinguishing  the  three  groups  into 
which  they  have  been  divided  in  Table  II. 

4.  By  what  characters  are  the  platinum  metals  as  a  class  chiefly 
marked  ?     Make  a  table  which  will  bring  into  comparison  the  dif- 
ferent double  chlorides  of  these  elements. 

5.  Explain,  on  the  principle  of  dialysis,  the  transmission  of  hydro- 
gen gas  through  the  walls  of  a  heated  palladium  or  platinum  tube. 

6.  Regarding  the  hydrogen  condensed  by  platinum  as  chemically 
combined  with  the  metal,  cannot  you  find  in  this  circumstance  an 
explanation  of  the  enhanced  energy  of  the  gas  when  in  this  condi- 
tion.    Consider  the  polarization  of  the  negative  platinum  plate  in  a 
voltaic  cell  as  an  illustration  of  the  same  principle. 


QUESTIONS  AND  PROBLEMS.  429 

7.  Show  in  what  way  the  platinic  salts  may  be  used  to  determine 
the  molecular  weight  of  an  organic  base,  and  give  an  illustration  of 
the  principle. 

8.  Write  the  reactions  by  which  platinic  sulphate  and  nitrate  may 
be  prepared. 

9.  Write  the  reaction  of  a  solution  of  platinic  chloride  on  a  solu- 
tion of  potassic  nitrate.     Platinic  nitrate  is  one  of  the  products. 

10.  Write  the  reaction  of  sodic  carbonate  on  a  solution  of  platinic 
sulphate,  assuming  that  the  chief  product  is  platinic  hydrate. 

11.  Write  the  reactions  by  which  platinous  hydrate  may  be  pre- 
pared. 

12.  When  platinous  chloride  dissolves  in  hydrochloric  acid  in  con- 
tact with  the  air,  what  is  the  reaction  ? 

13.  Make  a  scheme  illustrating  the  constitution  or  relations  of  the 
more  important  compounds  of  the  platinum  bases. 

14.  Explain  a  method  of  separating  the  platinum  metals  from 
each  other. 


430  TITANIUM.  [§  368. 


Divisions  XVII.  to  XIX. 

368.  TITANIUM.    Ti  =  50.  —  Tetrad.      No  compounds 
corresponding  to  a  lower  degree  of  quantivalence  are  with  cer- 
tainty known.     A  comparatively  rare  element,  but  not  unfre- 
quently  associated  with  iron.     The  most  abundant  native  com- 
pound is  Menaccanite  or  Titaniferous  Iron,  whose  symbol  has 
already  been  given  among  the  iron  ores.     This  mineral,  how- 
ever, is  in  most  cases  an  isomorphous  mixture  of  ( Ti~Fe)  03 
and  Fe%0s,  sometimes  containing  also  magnesium  and  manga- 
nese, and  thus  arise  the  numerous  varieties  which  have  been 
distinguished.     The  other  important  compounds  are 

Rutile,  Brookite,  and  Octahedrite  (2d  or  4th  System)          Ti  02, 
Perofskite  (Rhombohedral)  Ca = Of  Ti  0, 

Sphene  (Monoclinic)  (Ca-0-Ti)zO£Si. 

Titanium  is  also  associated  with  columbium,  tantalum,  cerium, 
yttrium,  and  zirconium  in  a  number  of  rare  minerals. 

369.  Metallic  Titanium  has  never  been  obtained  as  a  mas- 
sive metal,  and  its  properties  are  very  imperfectly  known.     As 
formed  by  decomposing  the  potassio-titanic  fluoride  with  potas- 
sium it  is  a  dark-green  powder,  showing  under  the  microscope 
the  color  and  lustre  of  iron.     In  this  condition  it  is  very  com- 
bustible, readily  dissolves  in  hydrochloric  acid,  and  even  decom- 
poses water  at  the  boiling-point. 

370.  Titanic  Chloride,  Ti  Cl±,  is  obtained  by  passing  chlorine 
gas  through  an  intimate  mixture  of  titanic  oxide  and  carbon  in- 
tensely heated.     It  is  a  heavy,  colorless  liquid,  boiling  at  135°, 
and  yielding  a  vapor  whose  Sp.  Gr.  =  98.65.     Exposed  to  the 
air  it  absorbs  moisture,  and  gradually  solidifies,  forming  a  crys- 
talline hydrate  which  readily  dissolves  in  water.     From  this 
solution,  if  sufficiently  dilute,  almost  the  whole  of  the  titanium 
is  precipitated  as  a  hydrate  on  boiling,  and  the  same  is  true  of 
the  solution  formed  by  dissolving  the  native  oxides  (after  fusion 
with  an  alkaline  carbonate)  in  hydrochloric  acid. 

371.  Titanous  Chloride,  Ti2Cl6,  is  formed  bypassing  a  mix- 
ture of  WiOl4  and  HI-HI  through  a  red-hot  porcelain  tube.    The 
compound  is  thus  obtained  in  dark  violet  scales,  which  readily 


§376.]  TITANIUM.  431 

dissolve  in  water  forming  a  violet  solution,  but  in  contact  with 
the  air  this  solution  gradually  loses  its  color  and  deposits  titanic 
hydrate.  The  same  color  is  produced  by  boiling  with  tin  a  so- 
lution of  titanic  oxide  in  hydrochloric  acid,  and  this  reaction  is 
the  best  test  for  titanium.  The  solution  of  titanous  chloride  is 
a  very  powerful  reducing  agent,  which  indicates  that  the  radical 
[  7Y2]1  is  not  a  stable  condition  of  the  element. 

372.  Titanic  Bromide,  and  Iodide,  TiBr±  and  TiI4,  are  fusi- 
ble and  volatile  crystalline  solids. 

373.  Titanic  Fluoride,  TiF±,  is  a  fuming,  colorless  liquid, 
obtained  by  distilling  a  mixture  of  fluor-spar  and  titanic  oxide 
with  sulphuric  acid.     This  compound  is  resolved  by  water  into 
soluble  hydro-titanic  fluoride  and  insoluble  titanic  oxyfluoride. 

374.  Hydro-titanic  Fluoride,  TiF4 .  ZHF,  is  the  acid  of  a 
large  class  of  salts  which  are  easily  made  from  the  solution  pro- 
duced as  just  stated.      The  ammonium  and  potassium  salts, 
which  are  the  most  important,  both  crystallize  in  white  anhy- 
drous scales. 

375.  Titanic  Hydrates.  —  A  large  number  of  these  hydrates 
have  been  distinguished,  and  they  affect  two  very  different  mod- 
ifications.    Those  obtained  by  precipitation  with  ammonia  read- 
ily dissolve  in  acids,  and  when  heated  are  converted  into  the 
anhydride  with  vivid  incandescence.     Those  obtained  by  boil- 
ing dilute  solutions  of  the  chloride  or  sulphate  are  insoluble  in 
all  acids  except  strong  sulphuric.     They  give  off  water  more 
readily  than  the  others,  and  the  dehydration  is  not  attended  by 
the  same  incandescence.     The  composition  of  these  hydrates 
depends  on  the  temperature  at  which  they  are  dried,  and  they 
may  be  regarded  as  derived  from  the  normal  hydrate  by  the 
method  repeatedly  illustrated  and  expressed  by  the  general 
equation 

nTiffo4  —  mff20  =  (OmTi^Ho^n.^,  [353] 

The  two  modifications  have  been  obtained  in  the  same  degrees  of 
hydration,  and,  so  far  as  known,  they  are  isomeric.     Moreover, 
by  dialysis  a  pure  aqueous  solution  of  "titanic  hydrate  has  been 
procured,  which  gelatinizes  when  concentrated,  and  evidently" 
contains  the  compound  in  a  colloidal  condition. 

376.  Titanic   Oxide,   TiO^,  is  chiefly  interesting  from  the 
fact  that  it  affects  three  different  modifications,  which  are  rep- 
resented in  nature  by  the  minerals  Rutile,  Brookite,  and  Octa- 


432  TITANIUM.  [§  377. 

hedrite.  These  three  isomeric  bodies  differ  from  each  other  in 
crystalline  form,  in  density,  and  in  hardness.  Rutile,  the  most 
abundant,  has  the  greatest  hardness  and  density.  Its  crystals 
are  tetragonal  and  isomorphous  with  those  of  Sn  02.  Brookite, 
which  stands  next  in  hardness  and  density,  affects  forms  of  the 
orthorhombic  system,  which  are  approximately  isomorphous  with 
those  of  Mn02.  Lastly,  Octahedrite  is  softer  and  less  dense 
than  either  of  the  others,  and  its  crystals,  although  tetragonal, 
differ  essentially  from  those  of  Rutile.  (Problem  2,  page  144.) 
The  same  differences  have  been  observed  in  crystals  obtained 
artificially  by  decomposing  TiF±  or  TiGl±  with  steam,  and  it  is 
found  that  the  nature  of  the  product  depends  on  the  temperature 
at  which  the  reaction  takes  place,  the  hardest  and  most  dense 
crystals  being  formed  at  the  highest  temperature. 

In  its  densest  condition  titanic  oxide  has  a  red  color,  and  is 
insoluble  in  all  acids ;  but  the  white  anhydride,  obtained  by  ig- 
niting titanic  hydrate,  is  converted  into  a  sulphate  when  heated 
with  strong  sulphuric  acid,  and  may  then  be  dissolved  in  water. 
The  native  oxides,  also,  may  be  rendered  soluble  by  fusion  with 
alkaline  carbonates  or  bisulphates.  It  melts  before  the  com- 
pound blow-pipe. 

377.  Titanous  Oxide,  Ti203,  is  obtained  as  a  black  powder 
•when  a  stream  of  hydrogen  is  passed  over  ignited  Ti02.     It 
dissolves  in  sulphuric  acid,  forming  a  violet  solution,  from  which 
the  alkalies  precipitate  a  brown  hydrate.     A  similar  reduction 
takes  place,  and  the  same  violet  color  is  produced,  when  Ti02  is 
dissolved  in  fused  borax  or  microcosmic  salt,  and  the  bead 
heated  before  the  blow-pipe  on  charcoal  in  contact  with  a  small 
globule  of  tin. 

378.  Titanic  Sulphide,  TiS2,  is  formed  in  large,  brass-yellow, 
lustrous  scales  when  a  mixture  of  IH^  and  ISPi®l4  is  passed 
through  a  glass  tube  heated  to  incipient  redness.     It  is  decom- 
posed by  water,  and  cannot,  therefore,  be  obtained  by  precipi- 
tation. 

379.  Nitrides.  —  Titanium  has  a  marked  affinity  for  nitro- 
gen, and  combines  with  it  in  several  proportions.     When  dry 
ammonia  gas  is  passed  over  TiCl4  it  is  rapidly  absorbed  with 
great  elevation  of  temperature,  and  the  resulting  brown-red 
powder  has  the  symbol  (H^N^Tiy^Cl^     This  compound,  heated 
in  a  stream  of  ammonia  gas,  yields  a  copper-colored  substance, 


§381.]  TIN.  433 


which  is  the  nitride  TizN^  and  this,  when  further  heated  in  a 
current  of  hydrogen,  is  converted  into  a  second  nitride  (Ti^N^) 
having  a  golden-yellow  color  and  metallic  lustre.  A  third  vio- 
let-colored nitride  has  the  symbol  TiN2.  Lastly,  the  very  hard 
copper-colored  cubic  crystals  sometimes  found  adhering  to  the 
slags  of  iron-furnaces,  and  formerly  mistaken  for  metallic  tita- 
nium, have  the  composition  expressed  by  the  symbol  7Y5(7A^. 

380.  TIN.    Sn  =  llS.  —  Bivalent  and  Quadrivalent.     The 
last  is  the  most  stable  condition.     The  only  valuable  ore  of  tin 
is  the  oxide  Sn02,  called  in   mineralogy  Cassiterite  or  Tin 
Stone,  and  this  is  found  at  but  few  localities,  chiefly  in  Corn- 
wall, Malacca,  Bolivia,  Australia,  Bohemia,  and  Saxony.     This 
element  is  also  an  essential  constituent  of  Tin  Pyrites  \_Zn,Fe~\, 
[  Cu^SfSn,  and  is  associated  with  columbium,  titanium,  zir- 
conium, &c.,  in  a  few  rare  minerals,  but  its  range  in  nature,  so 
far  as  known,  is  very  limited. 

The  metal  is  obtained  by  reducing  the  native  oxide  with  coal  ; 
but,  although  in  theory  so  simple,  this  process  is  in  practice  quite 
complicated.  The  ore  requires,  previous  to  smelting,  a  pro- 
longed mechanical  treatment,  and  in  the  furnace  a  large  amount 
of  metal  passes  into  the  slags,  which  therefore  have  to  be  worked 
over. 

381.  Metallic  Tin  has  a  familiar  white  color  and  bright  lustre. 
It  has  a  crystalline  structure,  and  the  breaking  of  the  crystals 
against  each  other,  when  a  bar  of  the  metal  is  bent,  produces 
the  peculiar  sound  known  as  the  cry  of  tin.     By  slowly  cooling 
the  fused  metal  distinct  crystals  can  be  obtained,  which  belong 
to  the  tetragonal  system.     The  tenacity  of  tin  is  feeble,  but  it 
can  readily  be  rolled  and  beaten  into  thin  leaves,  which  are 
well  known  under  the  name  of  tin-foil.    Sp.  Gr.  =  7.3.   .Melts 
at  222°.     Boils  at  a  white  heat.     Inferior  conductor  of  heat  or 
electricity. 

Tin  does  not  tarnish  in  a  moist  atmosphere  which  is  free- 
from  sulphur,  but  when  melted  in  the  air  it  slowly  oxidizes,  and 
at  a  red  heat  decomposes  steam.  Hydrochloric  acid  dissolves 
the  metal  rapidly,  the  products  being  stannous  chloride  and  hy- 
dro^en  gas.  It  also  dissolves  slowly  when  boiled  with  dilute 

O  O  J 

sulphuric  acid,  yielding  stannous  sulphate  and  liberating  hydro- 
gen as  before.     When  the  sulphuric  acid  is  concentrated,  S02 
is  evolved  and  stannous  sulphate  formed  only  so  long  as  the  tia 
19  SB 


434  TIN.  [§382. 

is  in  excess.  If  the  acid  is  in  excess,  sulphur  separates  and  the 
product  is  stannic  sulphate.  Very  strong  nitric  acid  does  not 
act  on  the  metal,  but  when  somewhat  diluted  it  converts  the 
tin  into  a  white  hydrate,  insoluble  in  an  excess  of  the  acid. 
Aqua-regia,  if  not  too  concentrated,  dissolves  tin  as  stannic 
chloride,  and  the  alkaline  hydrates  and  nitrates  also  act  upon  it 
at  a  high  temperature. 

Tin  unites  directly  with  most  of  the  non-metallic  elements, 
and  forms  alloys  with  many  of  the  metals.  The  alloys  with 
copper  have  already  been  mentioned.  Pewter  and  plumber's 
solder  are  alloys  of  tin  and  lead.  Britannia  metal,  an  alloy  of 
brass,  tin,  lead,  and  bismuth,  and  the  silvering  of  mirrors  an 
amalgam  of  tin  and  mercury.  On  account  of  its  beautiful  lustre 
and  power  of  resisting  atmospheric  agents,  tin  is  much  used  for 
coating  other  metals.  The  common  tin  ware  is  made  of  sheet- 
iron  thus  protected. 

382.  Stannous  Chloride.  Sn  O12.  —  The  anhydrous  com- 
pound (butter  of  tin)  obtained  by  heating  mercuric  chloride 
with  an  excess  of  tin,  or  by  heating  the  metal  in  hydrochloric 
acid  gas,  is  a  fusible  white  solid  with  a  fatty  lustre,  soluble  in 
water  and  alcohol.  The  hydrous  salt  (tin  salts),  formed  by 
crystallizing  the  solution  of  tin  in  hydrochloric  acid,  has  the 
symbol  SnCl2  .  2ZT20.  The  pure  crystals  dissolve  perfectly  in 
a  small  amount  of  water,  free  from  air,  but  a  large  amount  of 
water  produces  a  partial  decomposition. 


(2SnCl2  +  3ff20  +  Aq)  = 

Sn2OCi2  .  2H2O  +  (2ffCl  +  Aq).  [354] 

So,  also,  when  the  solution  is  exposed  to  the  air. 

(GSnCl2  +  ±H20  +  Aq)  +  ©=©  = 

2(Sn2OCI2  .  2H20)  +  (2SnOl,  +  Aq).  [355] 


The  oxychloride,  which  is  milk  white  and  insoluble  (even  in 
dilute  acids),  renders  the  solution  in  both  cases  turbid.  Free 
hydrochloric  acid,  tartaric  acid,  and  sal  ammoniac  prevent  the 
decomposition.  Owing  to  the  unsatisfied  affinities  of  the  tin 
radical,  stannous  chloride  is  a  powerful  reducing  agent  (277), 
and  is  much  used  for  this  purpose  both  in  the  laboratory  and 
the  dye-house.  It  also  acts  as  a  mordant.  Lastly,  it  forms 
salts  with  several  of  the  metallic  chlorides. 


§383.]  TIN.  f  435 

Potassio-stannous  Chloride        SnCl2 .  2KCI .  (1, 2,  or  3ff20), 
Bario-stannous  Chloride  Sn  C12  .  Ba  C12 .  4ff2  0. 

383.  Stannic  Chloride,  Sn  C14,  may  be  made  either  by  dis- 
tilling a  mixture  of  tin  and  mercuric  chloride,  the  last  being  in 
excess,  or  by  heating  tin  in  chlorine  gas.  It  is  a  colorless,  fum- 
ing liquid,  boiling  at  115°,  and  yielding  a  vapor  whose  Sp.  Gr. 
=  132.7.  The  liquid,  exposed  to  the  air,  eagerly  absorbs  moist- 
ure, and  changes  into  a  crystalline  solid.  When  mixed  with 
water  intense  heat  is  evolved,  and  a  solution  formed  which  yields 
on  evaporation  rhombohedral  crystals  of  SnOl4  .  5ff20.  These 
crystals,  dried  in  vacua,  lose  3ff20,  and  there  is  reason  to  be- 
lieve that  the  remaining  2ff2  0  are  a  part  of  the  molecule  of  the 
salt.  If  we  regard  the  atoms  of  chlorine  as  trivalent,  we  can 
easily  see  that  such  an  atomic  group  would  be  possible,  for  we 
might  then  have  the  univalent  radical  (H-  Cl=  Cl)  =  Hd  re- 
placing Ho,  and  the  symbol  of  the  dried  salt  would  be  written 
Sn^Ho2,ffcl2.  The  same  principle  may  be  applied  in  other 
cases  where  the  violence  of  the  action  indicates  that  a  chemical 
union  has  taken  place  between  an  anhydrous  chloride  and  water. 
Such  bodies,  however,  may  also  be  regarded  as  chlorhydrines 
(349),  to  which  molecules  of  HCl  are  united  in  place  of  water 
of  crystallization.  Thus  the  symbol  of  the  hydrous  chloride  we 
have  been  discussing  might  be  written  Sn^Cl2,Ho2 .  2ITCL 

Although  stannic  chloride  forms  a  clear  solution  with  a  small 
amount  of  water,  copious  dilution  determines  the  precipitation 
of  the  greater  part  of  the  tin  as  an  insoluble  stannic  hydrate. 
Heat  favors  this  decomposition,  and,  on  the  other  hand,  the  pres- 
ence of  a  large  excess  of  hydrochloric  acid  prevents  it.  Stan- 
nic chloride  unites  with  a  considerable  number  of  bodies  both 
organic  and  inorganic,  and  forms  double  salts  with  several  of 
the  metallic  chlorides.  Ammonio-stannic  chloride,  Sn  C74  . 
1NH±Cl  (pink  salts  of  the  dyers)  is  isomorphous  with  the  cor- 
responding compound  of  platinum.  An  impure  solution  of 
stannic  chloride,  made  by  dissolving  tin  in  aqua-regia,  is  also 
extensively  used  in  dyeing  for  brightening  and  fixing  certain 
red  colors. 

There  are  two  bromides  and  iodides  of  tin  corresponding  to 
the  chlorides.  There  is  also  a  stannous  fluoride,  and  although 
stannic  fluoride  has  not  been  isolated,  a  large  number  of  double 


436  TIN.  [§384. 

stannic  fluorides  or  fluostannates  are  known,  which  are  isomor- 
phous  with  the  corresponding  compounds  of  titanium  and  silicon. 

384.  Stannous  Hydrate.  —  The  precipitate  which  falls  on 
adding  an  alkaline  carbonate  to  a  solution  of  stannous  chloride 
is  said  to  have  the  composition  JBof(iSlnfO).     It  is  soluble  in 
both  alkalies  and  acids.     Boiled  with  water  or  a  weak  solution 
of  potash  it  is  rendered  anhydrous,  but  if  boiled  with  a  concen- 
trated solution  of  this  alkali  it  yields  potassic  stanriate  and  me- 
tallic tin.     The  moist  hydrate  absorbs  oxygen  from  the  air,  and 
acts,  like  the  chloride,  as  a  reducing  agent.     The  only  impor- 
tant oxygen  salt  corresponding   to  this   hydrate  is  stannous 
sulphate.     • 

385.  Stannic  Hydrate,  like  titanic  hydrate,  affects  both  a 
soluble  and  an  insoluble  modification.    The  hydrate  precipitated 
when  ammonia  is  added  to  a  solution  of  stannic  chloride  dis' 
solves  readily  both  in  acids  and  alkalies,  while  that  obtained  by 
boiling  the  same  solution  greatly  diluted,  or  by  acting  on  tin 
with  nitric  acid,  is  insoluble  in  acids,  and  dissolves  less  readily 
than  the  first  in  alkalies.      The  composition  of  these  bodies 
varies  with  the  temperature  at  which  they  are  dried,  and  they 
are  usually  distinguished  as  stannic  and  meta-stannic  hydrates. 
Like  the  corresponding  compounds  of  titanium,  they  may  be 
regarded  as  derived  from  a  normal  hydrate  of  either  class  by 
the  elimination  of  successive  molecules  of  water.     The  salts  ob- 
tained by  dissolving  stannic  hydrate  in  oxygen  acids  are  unim- 
portant.    The  sulphate  is  the  most  stable,  but  this  is  completely 
decomposed,  and  the  tin  precipitated  as  meta-stannic  hydrate 
when  the  aqueous  solution  is  diluted  and  boiled.     The  atoms 
Sn=  form  much  more  stable  compounds  when  they  act  as  acid 
radicals.     The  alkaline  stannates  crystallize  readily,  and  both 
potassic  and  sodic  stannates,  (K  or  Na)2=OfSnO  .  4//20,  are 
commercial  products  much  used  as  mordants.     Their  efficacy 
depends  on  the  fact  that  ammonic  chloride  and  all  acids,  even 
the  C02  of  the  atmosphere,  decomposes  these  salts  when  in  so- 
lution, and  the  stannic  hydrate  thus  precipitated  in  the  fibre  of 
the  cloth  binds  the  coloring  matter. 

The  compounds  obtained  by  dissolving  meta-stannic  hydrate  in 
alkaline  solvents  cannot  be  crystallized,  but  are  precipitated  on 
adding  to  the  solution  caustic  potash.  The  potassium  salt  thus 
obtained,  dried  at  126°,  has  the  composition  K2=  OfSn&  09 . 


§387.]  TIN.  437 

It  was  formerly  supposed  that  the  peculiar  qualities  of  the 
meta-stannic  hydrates  and  the  meta-stannates  were  due  to  the 
atomic  grouping  here  represented,  but  this  opinion  has  not  been 
sustained  by  recent  investigations.  The  water  represented  as 
water  of  crystallization  cannot  be  removed  without  decomposing 
the  salt,  and  is  evidently  water  of  constitution  ;  so  that  we  have 
good  reason  for  writing  the  symbol  H^K^x. 0^(8^0^)  after  the 
type  of  the  normal  stannates,  and  we  may  regard  it  as  an  ex- 
ample of  the  soluble  colloidal  hydrates,  to  which  we  have  before 
referred  (337).  This  view  harmonizes  with  the  facts  that  on 
boiling  an  aqueous  solution  of  this  compound  meta-stannic  hy- 
drate is  precipitated,  and  that  by  dialysis  a  solution  both  of 
meta-stannic  and  stannic  hydrates  in  pure  water  may  be  ob- 
tained. The  two  classes  of  compounds  are  probably  isomeric, 
but  differ  in  the  degree  of  molecular  condensation. 

386.  Oxides.  —  Stannous  Oxide,  SnO,  may  be  obtained  in 
various  ways,  and  its  color  differs  according  to  the  mode  of 
preparation.     It  has  a  strong  affinity  for  oxygen,  and  if  set  on 
fire  when  dry  burns  to  stannic  oxide. 

Stannic  oxide  has  been  crystallized  artificially,  not  only  in  the 
forms  of  Tin-stone  isomorphous  with  Rutile,  but  also  in  forms 
isomorphous  with  Brookite.  As  obtained  by  igniting  the  hy- 
drate, or  by  burning  metallic  tin,  it  is  an  amorphous  white  pow- 
der. It  offers  even  greater  resistance  to  the  action  of  chemical 
agents  than  Ti0.2.  It  is  not  attacked  by  acids  even  when  con- 
centrated. It  is  not  dissolved  by  fusion  with  alkaline  carbon- 
ates, but  is  rendered  soluble  by  fusion  with  caustic  alkalies.  It 
is  al.-o  taken  up  when  fused  with  acid  potassic  sulphate,  but 
separates  completely  when  the  fused  mass  is  dissolved  in  water. 
Moreover,  like  titanic  oxide  it  is  very  hard  and  infusible,  but 
unlike  that  it  is  reduced  to  the  metallic  state  when  ignited  in 
a  stream  of  hydrogen  gas. 

Besides  SnO  and  SnO2  an  intermediate  oxide,  Sn20s,  has 
been  distinguished,  but  it  does  not  form  definite  salts.  Dissolved 
in  hydrochloric  acid  it  gives  with  auric  chloride  the  beautiful 
purple  precipitate  known  as  Purple  of  Cassius  (147). 

387.  Sulphides.  —  The  dark -brown  precipitate  which  falls 
when  ff.2S  is  passed  through  an  acid  solution  of  a  stannous  salt 
is  SnS,  and  the  dull  yellow  precipitate  which  forms  under  the 
same  circumstances  in  a  solution  of  a  stannic  salt  is  a  hydrate 


438  TIN.  [§388. 

of  SnS2.  The  last  of  these  dissolves  readily  m  solutions  of  al- 
kaline sulphides,  and  forms  with  them  definite  salts.  It  is  also 
soluble  in  the  fixed  alkaline  hydrates,  and  in  either  case  is  pre- 
cipitated unchanged  when  the  alkali  is  neutralized  with  an  acid. 
Stannous  sulphide,  on  the  other  hand,  does  not  form  salts  with 
the  alkaline  sulphides,  and  does  not  dissolve  in  solutions  of  these 
compounds,  unless,  like  the  common  yellow  ammonic  sulphide, 
they  contain  an  excess  of  sulphur,  when  it  is  converted  into 
SnSft  and  as  such  is  precipitated  on  neutralizing  the  alkali. 
It  does,  however,  dissolve  in  the  fixed  alkaline  hydrates,  but 
when  an  excess  of  acid  is  added  to  the  solution  a  yellow  pre- 
cipitate of  SnS2  falls,  containing  only  one  half  of  the  tin  present. 

The  beautiful  yellow  flaky  material  known  as  mosaic  gold, 
and  used  in  painting  to  imitate  bronze,  consists  of  anhydrous 
stannic  sulphide,  and  is  obtained  by  subliming  a  mixture  of  tin, 
sulphur,  sal-ammoniac,  and  mercury.  There  is  also  a  sesqui- 
sulphide,  Sn2S3. 

388.  Compounds  with  the  Alcohol  Radicals.  —  These  com- 
pounds are  very  numerous  and  highly  important,  theoretically, 
because  they  establish  beyond  all  doubt  the  atomic  relations  of 
tin.  Compounds  have  been  obtained  containing  methyl,  ethyl, 
and  amyl,  either  singly  or  associated  together.  Three  com- 
pounds are  known  containing  only  tin  and  ethyl.  Putting 
Et  =  (C2ff5)  we  have 


All  three  are  colorless  oily  liquids.  The  last  is  the  most  stable, 
boiling  at  181°,  and  yielding  a  vapor  whose  Sp.  Gr.  =  116. 
The  others  cannot  be  volatilized  without  decomposition,  and 
unite  directly  with  oxygen,  chlorine,  bromine,  and  iodine.  The 
first,  especially,  like  other  stannous  compounds,  acts  as  a  redu- 
cing agent,  absorbing  oxygen  from  the  air,  and  precipitating  sil- 
ver from  a  solution  of  the  nitrate.  This  is  the  only  stannous 
compound  known  among  this  class  of  bodies.  In  all  the  others 
the  tin  atoms  exert  their  maximum  atom-fixing  power,  and  they 
may  be  regarded  either  as  compounds  of  the  radicals  (SnEt2)= 
or  (SnEt^)-,  or  else  as  formed  from  stannic  ethide  by  replacing 
either  one  or  more  of  the  atoms  of  ethyl  by  other  radicals. 
The  following  are  a  few  examples  :  — 


§391.]  ZIRCONIUM.  439 


Stanno-diethylic  Bromide 

Stanno-diethy  lie  Oxide  (SnJEt.2)=0, 

Stanno-diethy  lie  Acetate  (SnM2)=  02=(  O2ffs  0)% 

Stanno-diethylic  Sulphate  (SnEt^)=OiS02l 

Stanno-triethylic  Chloride  (SnM3)-  Cl, 

Stanno-triethylic  Hydrate  (SnEtsyO-H, 

Stanno-triethylic  Oxide  (SnEts)2=0, 

Stanno-triethylic  Carbonate  (SnEt^O^GO.     v 

The  methyl  and  amyl  compounds  are  formed  after  the  same 
analogy,  and  also  others  which  contain  both  methyl  and  ethyl. 
These  compounds  are  either  liquids  or  crystalline  solids.  The 
chlorides,  bromides,  and  iodides  are,  as  a  rule,  volatile  and  spar- 
ingly soluble  in  water.  The  oxides  and  oxygen  salts,  on  the 
other  hand,  generally  dissolve  freely  in  water,  and  are  more 
easily  decomposed  by  heat.  The  vapor  densities  of  several  of 
these  compounds  are  given  in  Table  III.,  and  this  list  might  be 
greatly  extended. 

389.  ZIRCONIUM.   Zr  =  89.6.  —  Tetrad.     Found  only 
in  Zircon,  Eudialyte,  and  a  few  other  very  rare  minerals.  The 
elementary  substance  closely  resembles  silicon.     It  may  be  ob- 
tained by  similar  reactions  in  three  corresponding  states,  amor- 
phous, crystalline,  and  graphitoidal.     Amorphous  zirconium  is 
a  very  combustible  black  powder.     The  crystals,  Sp.  Gr.  4.15, 
resemble  antimony  in  color,  lustre,  and  brittleness,  and  burn 
only  at  a  very  high  temperature.     The  graphitoidal  variety 
forms  very  light  steel-gray  scales.     Zirconium  is  very  infusible, 
is  but  slightly  attacked  by  the  ordinary  acids,  but  hydrofluoric 
acid,  and  in  some  conditions  aqua-regia,  dissolve  it  rapidly. 

390.  Zirconic  Chloride,  ZrClA,  is  a  white  volatile  solid  (Sp. 
Gr.  =  117.6),  which  dissolves  easily  and  with  evolution  of  heat 
in  water.     This  solution,  or  the  solution  of  the  hydrate  in  hy- 
drochloric acid,  yields  on  evaporation  a  large  mass  of  white 
silky  needles,  which,  when  heated,  lose  water  and  hydrochloric 
acid,  leaving  an  oxychloride,  Zr9O4Ol^ 

391.  Zirconic  Fluoride,  ZrF#  is  likewise  a  volatile  white 
solid,  and  forms  a  crystalline  hydrate,  ZrF±  .  Sff20,  which  is 
decomposed  by  heat,  leaving  pure   ZrOf      Zirconic  fluoride 
unites  with  many  other  metallic  fluorides,  forming  salts  which 
are  isomorphous  with  the  corresponding  compounds  of  silicon, 


440  ZIRCONIUM.  [§392. 

titanium,  and  tin.     The  following  symbols  illustrate  the  known 
types :  — 

Cadmio-zirconic  Fluoride  ZrF± .  2CdF2  .  6#20, 

Tripotassio-zirconic  Fluoride  ZrF± .  3KF, 

Dipotassio-zirconic  Fluoride  ZrF4  .  21fF, 

Potassio-zirconic  Fluoride  ZrF± .  KF .  ff20, 

Sodio-zirconic  Fluoride  2ZrF4 .  5NaF. 

392.  Zirconic  Hydrate,  precipitated  from  the  chloride  by 
ammonia,  and  dried  at  17°,  has  the  symbol  Zr^ffo4.     Dried  at 
a  higher  temperature,  (ZrO)=ffe2'     It  i§  a  yellowish,  translu- 
cent, gummy  mass,  having  a  conchoidal  fracture.     The  hydrate 
precipitated  and  washed  cold  dissolves  easily  in  acids,  and,  very 
slightly,  even  in  water;  but  when  precipitated  from  hot  solu- 
tions, or  washed  with  hot  water,  it  dissolves  only  in  concen- 
trated acids.    Zirconic  hydrate  acts  both  as  a  base  and  an  acid. 

There  are  several  zirconic  sulphates.  The  normal  salt  can 
be  crystallized,  and  the  formation  of  a  basic  sulphate,  which  is 
precipitated  when  a  neutral  solution  of  zirconia  in  sulphuric 
acid  is  boiled  with  potassic  sulphate,  is  one  of  the  most  charac- 
teristic reactions  of  zirconium.  The  salts  of  zirconium  have  an 
astringent  taste,  and  the  solutions  redden  turmeric  paper. 

The  precipitated  hydrate  is  insoluble  in  caustic  alkalies,  but 
when  precipitated  by  a  fixed  alkaline  carbonate,  or,  better,  by  a 
bicarbonate,  it  dissolves  in  an  excess  of  the  reagent.  The  alka- 
line zirconates  can  be  obtained  by  fusion,  and  several  definite 
crystalline  zirconates  of  the  more  basic  radicals  have  been 
studied. 

393.  Zirconic  Oxide  (Zirconia),  Zr02,  is  obtained  by  heat- 
ing the  hydrate.     Prepared  at  the  lowest  possible  temperature 
it  forms  a  white  tasteless  powder  soluble  in  acids ;  but  when 
heated  to  incipient  redness  it  glows  brightly,  becomes  denser 
and  much  harder,  and  is  then  insoluble  in  any  acid  excepting 
hydrofluoric  and  strong  sulphuric.     Zirconia  has  been  crystal- 
lized artificially  in  the  same  form  as  Tin-stone  and  Rutile. 

The  mineral  zircon  is  usually  regarded  as  a  silicate  of  zirco- 
nium, Zr^OfSi,  but  the  symbol  may  also  be  written  {j8r'J9Fj*0* 
and  this  view  harmonizes  with  the  fact  that  the  crystalline  form 
•is  almost  identical  with  that  of  ZrO^  SnO^  and  fVOj.  More- 


§394.J  QUESTIONS  AND  PROBLEMS.  441 

over,  several  isomorphous  varieties  of  this  mineral  are  known 
(Malacone,  Oerstedite,  &c.)  in  which  the  proportions  of  Zr  and 
Si  are  quite  variable.  They  are  more  or  less  hydrous,  and  for 
the  most  part  comparatively  soft,  but,  like  pure  Zr  02,  they  be- 
come, when  heated,  exceedingly  hard  as  well  as  more  dense. 

394.  THORIUM.  Th  =  115.7.—  The  mineral  Thorite,  or 
Orangeite,  is  essentially  a  hydrous  silicate  of  this  exceedingly 
rare  metallic  element,  which  has  also  been  found,  but  only  as  a 
subordinate  constituent,  in  Euxenite,  Pyrochlore,  Monazite, 
Gadolinite,  and  Orthite.  When  Thorite  is  decomposed  by  hy- 
drochloric acid  a  solution  of  thoric  chloride,  Th  Cl±,  is  obtained, 
from  which  the  caustic  alkalies  precipitate  a  hydrate  insoluble 
in  an  excess  of  the  reagent.  A  similar  precipitate  is  obtained 
with  the  alkaline  carbonates,  but  this  readily  dissolves  when  an 
excess  is  added  to  the  solution.  In  the  same  solution  a  precip- 
itate is  obtained  with  oxalic  acid,  potassic  sulphate,  and  potassic 
ferro-cyanide. 

As  the  above  reactions  indicate,  Thorium  is  allied  in  many 
of  its  properties  to  the  metals  of  the  glucinum  and  cerium 
groups,  but  in  other  respects  it  resembles  more  nearly  zirco- 
nium, with  which  it  is  here  associated.  The  anhydrous  oxide 
Th02  is  a  white  powder,  which  glows  when  heated,  becomes 
more  dense,  and  after  ignition  is  insoluble  in  any  acid  except 
concentrated  sulphuric.  It  has  a  high  specific  gravity,  and  by 
fusion  with  borax  has  been  obtained  in  tetragonal  crystals  (Fig. 
37)  resembling  those  of  Tin-stone,  Sn02,  and  Rutile,  Ti02. 
The  anhydrous  chloride  is  volatile,  and  the  hydrated  chloride 
forms  a  radiate  crystalline  mass  like  Zr  C74.  The  chloride  may 
be  reduced  by  sodium,  and  the  metal  may  be  thus  obtained  as 
a  gray  lustrous  powder  which  readily  burns  in  the  air. 


Questions  and  Problems. 
Titanium. 

1.  Compare  by  means  of  graphic  symbols  the  composition  of  Pe- 
rofskite  and  Menaccanite.     Can  they  be  regarded  as  similarly  con- 
stituted ? 

2.  Write  the  reaction  by  which  titanic  chloride  is  made. 

3.  According  to  the  experiments  of  Isidore  Pierre,  0.8215  gramme 

19* 


442  QUESTIONS  AND  PROBLEMS. 

of  TiCl4  yield  2.45176  grammes  of  AgCL  Calculate  the  atomic 
weight  of  titanium,  and  state  clearly  the  course  of  reasoning  by 
which  the  result  is  reached.  Ans.  50.34. 

4.   Write  the  reaction  which  takes  place  when  a  dilute  aqueous 
solution  of  TiCl  is  boiled. 


5.  Write  the  reactions  which  take  place  when  a  solution  of  titanif- 
erous  iron  in  hydrochloric  acid  is  boiled  with  tin,  and  explain  the 
use  of  this  reaction  as  a  test  for  titanium. 

6.  Write  the  reaction  by  which  TiF+  is  prepared,  and  also  show 
how  it  is  decomposed  by  water. 

7.  Represent  the  constitution  of  hydro-titanic  fluoride  by  a  graphic 
symbol,  assuming  that  F  is  trivalent. 

8.  Represent  in  a  tabular  form  the  possible  titanic  hydrates. 

9.  Do  the  hydrates  of  any  of  the  preceding  elements  present  phe- 
nomena similar  to  those  of  titanic  hydrate  ? 

10.  Write  the  reaction  by  which  TiS^  is  prepared,  and  also  the 
reactions  by  which  crystals  of  TiOz  may  be  obtained. 

11.  Compare  the  specific  gravities  and  hardness  of  the  native  ti- 
tanic oxides.     What  would  these  differences  indicate  in  regard  to 
the  molecular  constitution  of  these  minerals  ? 

12.  Represent  by  graphic  symbols  the  constitution  of  the  nitrides 
of  titanium. 

13.  Point  out  the  analogies  between  titanium  and  the  platinum 
metals.     Is  titanium  in  any  way  related  to  iron  ? 

Tin. 

14.  Write  the  reactions  of  hydrochloric,  nitric,  and  sulphuric  acids 
on  metallic  tin. 

15.  Write  the  reaction  of  stannous  chloride  on  solution  of  HgClr 

16.  Write  the  reaction  by  which  anhydrous  SnClz  is  prepared. 

17.  Analyze  reactions  [354]  and  [355],  and  explain  the  use  of 
tin  salts  as  a  mordant. 

18.  Write  the  reactions  by  which  anhydrous  SnCl^  is  prepared. 

19.  Represent  the  constitution  of  hydrous  stannic  chloride  by 
graphic  symbols,  and  apply  the  same  principle  to  the  interpretation 
of  other  similar  compounds. 

20.  Write  the  reaction  when  a  dilute  aqueous  solution  of  stannic 
chloride  is  boiled,  and  explain  the  use  of  this  solution  as  a  mordant. 

21.  Write  the  reaction  which  takes  place  when  stannous  hydrate 
is  boiled  with  a  concentrated  solution  of  potassic  hydrate. 


QUESTIONS  AND  PROBLEMS.  443 

22.  Make  a  table  exhibiting  the  possible  stannic  hydrates,  and 
explain  the  difference  between  the  two  classes  of  these  compounds. 

23.  Write  the  reaction  which  takes  place  when  a  dilute  aqueous 
solution  of  stannic  sulphate  is  boiled.  « 

24.  Write  the  reaction  which  takes  place  when  a  solution  of  sodic 
stannate  is  boiled  with  ammonic  chloride. 

25.  Represent  the  constitution  of  meta-stannic  hydrate  by  graphic 
symbols,  and  explain  the  two  opinions  which  have  been  entertained 
in  regard  to  it,  showing  how  far  they  are  sustained  by  facts. 

26 .  Write  the  reaction  of  HZS  on  a  solution  of  stannous  or  stannic 
chloride. 

27.  Write  the  reaction  which  takes  place  when  SnS  is  dissolved 
in  yellow  ammonic  sulphide,  and  that  which  follows  on  neutralizing 
the  alkaline  solvent  with  an  acid.    Write  also  the  reactions  when  an 
alkaline  hydrate  is  used  as  the  solvent. 

28.  Point  out  the  analogies  and  the  differences  between  tin  and 
titanium.     By  what  simple  reaction  may  the  two  elements  be  sepa- 
rated when  in  solution  ? 

29.  How  is  tin  related  to  the  platinum  metals? 

30.  According  to  the  experiments  of  Dumas,  100  parts  of  tin, 
when  oxidized  by  nitric  acid,  yield  127.105  parts  of  Sn02.     What  is 
the  atomic  weight  of  the  element,  assuming  that  the  oxide  has  the 
constitution  represented  by  the  symbol  ?  Ans.  118.06. 

31.  On  what  facts  do  the  conclusions  in  regard  to  the  atomicity 
of  tin  and  the  constitution  of  its  several  compounds  rest  ? 

32.  Show  that  the  atomic  weight  of  tin,  deduced  from  the  percent- 
age composition  and  vapor  densities  of  its  compounds  with  the  alco- 
hol radicals,  agrees  with  the  value  given  above.     Show,  also,  that 
these  compounds  fully  illustrate  the  atomic  relations  of  the  elements. 

33.  State  the  reasons  for  classing  zirconium  and  thorium  with  tin 
and  titanium. 

34.  Point  out  the  resemblances  between  zirconium  and  silicon, 
and  give  the  reasons  for  classing  zircon  with  tin-stone  and  rutile. 


444  SILICON.  [§395. 


Division  XX. 

395.  SILICON.   Si  =  28.  —  Tetrad.     Most  abundant  of 
the  elements  after  oxygen,  forming,  as  is  estimated,  about  one 
fourth  of  the  rocky  crust  of  the  globe.      Always   found  in 
nature  united  to  oxygen  either  as  quartz,  Si02,  or  associated 
with  more  basic  radicals  in  the  various  native  silicates,  many 
of  whose  symbols  have  already  been  given  (333)  (352).     The 
elementary  substance  may  be  obtained  in  three  different  condi- 
tions, —  amorphous,  graphitoidal,  and  crystalline. 

1.  By  decomposing  SiF4  .  2AjPwith  potassium  or  sodium, 
or  by  heating  the  same  metals  in  a  current  of  the  vapor  of 
SiClto  silicon  is  obtained  as  a  dull-brown  powder,  which  soils 
the  fingers,  and  readily  dissolves  in  hydrofluoric  acid  or  a  warm 
solution  of  caustic  potash,  although  insoluble  in  water  and  the 
common  acids.    When  ignited  it  burns  brilliantly,  but  the  grains 
soon  become  coated  with  a  varnish  of  melted  silicon,  which  pro- 
tects them  from  the  further  action  of  the  air. 

2.  The  brown  powder  just  described,  when  intensely  heated 
in  a  closed  crucible,  becomes  very  much  denser  and  darker  in 
color,  and  afterwards  is  insoluble  in  hydrofluoric  acid,  and  does 
not  burn  even  in  the  oxyhydrogen  flame.     It  does  dissolve, 
however,  in  a  mixture  of  hydrofluoric  and  nitric  acids,  or  in 
fused  potassic  carbonate,  and  it  deflagrates  if  intensely  heated 
with  nitre.      \ 

3.  At  the  highest  temperature   of  a  wind-furnace  silicon 
melts,  and  may  be  cast  into  bars  which  have  a  crystalline  struc- 
ture, a  sub-metallic  lustre,  and  a  dark  steel-gray  color.     More- 
over, by  reducing  silicon  in  contact  with  melted  aluminum  or 
zinc  the  molten  metal  dissolves  the  silicon,  and  afterwards,  on 
cooling,  deposits  it  in  definite  crystals.     These  crystals  have  a 
reddish  lustre  and  the  form  of  diamond,  which  they  almost  rival 
in  hardness. 

396.  Silicic  Anhydride  or  Silica.    Si02.  —  By  far  the  most 
abundant  of  all  mineral  substances.     The  mineralogists  distin- 
guish two  principal  modifications,  Quartz  and  Opal.     Quartz 
crystallizes  in  the  hexagonal  system  (Figs.  64  to  67),  has  a  Sp. 
Gr.  2.5  to  2.8,  is  so  hard  that  it  cannot  be  cut  with  a  file,  and 
even  in  powder  is  but  slightly  acted  on  by  hot  solutions  of  caus- 


§397.]  SILICON.  445 

tic  alkalies.  Opal  is  amorphous  or  colloidal,  has  a  Sp.  Gr.  1.0 
to  2.3,  is  easily  abraded  with  a  file,  and  dissolves  in  alkaline  so- 
lutions. Each  of  these  mineral  species  exhibits  numerous  va- 
rieties, determined  by  differences  of  structure  or  admixtures  of 
different  bodies.  Among  those  of  quartz  may  be  mentioned 
common  quartz,  milky  quartz,  smoky  quartz,  amethyst,  chal- 
cedony, carnelian,  agate,  onyx,  flint,  hornstone,  jasper,  sand- 
stone, and  sand.  Among  those  of  opal  we  have  precious  opal, 
common  opal,  jasper  opal,  wood  opal,  siliceous  sinter,  float-stone, 
and  tripoli.  These  two  conditions  of  Si  0%,  however,  are  some- 
times found  alternating  on  the  same  specimen,  and  the  chalce- 
donic  varieties  of  quartz  have  frequently  the  appearance  of  opal, 
through  which  state  they  probably  passed  in  the  process  of  for- 
mation. The  opals  are  more  or  less  hydrous,  but  the  water 
present  is  usually  regarded  as  unessential. 

Both  in  its  crystalline  and  in  its  amorphous  condition  silica 
is  insoluble  in  water  and  in  all  acids  excepting  hydrofluoric 
acid,  which  is  its  appropriate  solvent.  The  heat  of  the  oxyhy- 
drogen  flame  is  required  for  its  fusion,  but  at  this  temperature 
it  melts  to  a  transparent  glass,  and  may  be  drawn  out  into  fine 
flexible  elastic  threads,  the  fused  silica  affecting  the  amorphous 
condition.  When  added  in  powder  to  melted  sodic  or  potassic 
carbonate  it  causes  violent  effervescence,  and  if  the  silica  is  pure 
the  product  is  a  colorless  glass.  Unless  the  silica  is  in  great 
excess  the  alkaline  silicates  thus  obtained  are  soluble  in  water, 
and  are  generally  known  as  soluble  or  water  glass.  They  yield 
alkaline  solutions,  which  are  very  much  used  in  the  arts, — 
1.  As  a  cement  for  hardening  and  preserving  stone;  2.  In  pre- 
paring walls  for  fresco-painting ;  3.  For  mixing  with  soap ;  and 
4.  In  preparing  mordanted  calico  for  dyeing.  The  same  solu- 
tions can  be  also  made  by  digesting  flints  in  strong  solutions  of 
the  caustic  alkalies  at  a  high  temperature  under  pressure. 

397.  Silicic  Hydrates.  —  If  to  a  solution  of  an  alkaline  sili- 
cate in  water  hydrochloric  acid  be  added  gradually,  a  gelatinous 
precipitate  of  silicic  hydrate  is  formed,  which,  in  its  initial  con- 
dition, probably  has  the  composition  Ho^Si ;  but  in  drying  it 
passes  through  every  degree  of  hydration,  and  the  various  hy- 
drates which  have  been  obtained  in  this  and  in  other  ways  may 
be  represented  by  the  general  formula 

nHo.Si  —  mR20  =  Ho^_^(OmSin).  [356] 


446  SILICON.  [§398. 

They  are  all,  however,  very  unstable  bodies,  some  losing  water 
at  low  temperatures,  and  others  very  hygroscopic,  so  that  it  is 
difficult  to  obtain  definite  compounds. 

If,  instead  of  making  the  experiment  as  just  directed,  a  dilute 
solution  of  an  alkaline  silicate  be  poured  into  a  considerable  ex- 
cess of  hydrochloric  acid,  no  precipitate  is  formed.  The  whole 
of  the  hydrate  remains  in  solution  mixed  with  the  alkaline  chlo- 
rides and  free  hydrochloric  acid.  These  crystalloid  substances, 
however,  can  readily  be  separated  by  dialysis  from  the  colloid 
hydrate,  and  a  pure  solution  of  silicic  hydrate  may  be  thus  ob- 
tained containing  as  much  as  five  per  cent  of  Si  02.  Moreover, 
by  boiling  in  a  flask  the  solution  may  be  concentrated,  until  the 
quantity  of  silica  reaches  fourteen  per  cent.  This  solution  is 
limpid,  colorless,  tasteless,  and  has  a  feebly  acid  reaction,  which 
a  very  small  quantity  of  K~Ho  is  sufficient  to  neutralize. 

Evidently,  then,  silicic  hydrate  has  both  a  soluble  and  an  in- 
soluble modification,  but  the  last  is  by  far  the  most  stable  con- 
dition. The  concentrated  solution,  formed  as  above,  in  a  few 
days  completely  gelatinizes.  Moreover,  even  in  a  closed  vessel 
this  jelly  gradually  shrinks,  spontaneously  squeezing  out  the 
greater  part  of  the  water,  until  at  last  it  becomes  a  hard  mass 
resembling  opal.  When,  however,  the  solution  is  quite  dilute, 
it  can  be  kept  indefinitely  without  gelatinizing,  and  most  spring 
and  river  waters  hold  an  appreciable  amount  of  silicic  hydrate 
thus  dissolved.  The  power  of  dissolving  silica,  which  natural 
waters  possess,  is  greatly  enhanced  by  the  presence  of  alkaline 
carbonates ;  and  when  the  action  of  the  alkaline  liquid  is  aided 
by  a  high  temperature,  as  in  the  case  of  hot  springs,  large 
quantities  of  silica  are  frequently  dissolved,  and  such  solutions 
have  undoubtedly  exerted  an  important  agency  in  the  geolog- 
ical history  of  the  earth.  Whenever  a  solution  of  silicic  hydrate 
is  evaporated  to  dryness,  the  whole  of  the  silica  is  rendered  in- 
soluble and  cannot  afterwards  be  dissolved  either  in  water  or 
common  acids. 

398.  Silicates. — Although  it  is  impossible  to  isolate  the 
numberless  intermediate  silicic  hydrates  comprehended  in  [356], 
yet  we  find  in  nature  numerous  mineral  silicates  formed  after 
the  same  types,  and  which  may  be  regarded  as  derived  from  the 
hydrates  by  replacing  the  hydrogen  atoms  with  various  basic 
radicals.  These  silicates,  like  silica  itself,  affect  both  the  crys- 
talline and  the  colloidal  condition. 


§398.]  SILICON.  '      447 

The  crystalline  silicates  are  represented  by  numerous  well- 
defined  mineral  species,  and  by  the  rocks  which  are  simply  ag- 
gregates of  such  minerals.  They  have  been  formed  in  many 
ways;  for  example,  —  1.  By  deposition  from  solution;  2.  By 
the  action  of  heated  water  or  vapor  on  igneous  and  sedimentary 
rocks ;  3.  By  the  slow  cooling  of  molten  siliceous  material. 

The  colloidal  silicates  are  represented  by  the  obsidians,  the 
pitch-stones,  and  other  volcanic  rocks,  which  have  probably  al- 
ways been  formed  by  the  sudden  cooling  of  melted  lavas.  To 
the  last  class  belong  also  the  various  artificial  silicates  we  call 
glass,  and  the  slags  obtained  in  many  metallurgical  processes. 
Thus  crown-glass  is  a  silicate  of  sodium  or  potassium  with  cal- 
cium, flint-glass  a  silicate  of  either  of  these  alkaline  radicals  with 
lead,  and  the  slags  silicates  of  calcium,  magnesium,  aluminum, 
and  iron  in  various  combinations.  Since  many  of  the  basic  hy- 
drates and  anhydrides  may  be  melted  with  silica  in  almost  every 
proportion,  we  do  not  find  in  the  colloidal  silicates  the  same 
definite  composition  as  in  the  crystalline  minerals,  but  they  are 
probably  in  all  cases  mixtures  of  definite  compounds. 

Most  of  the  silicates  are  fusible,  and  their  fusibility  is  in- 
creased by  mixture  with  eacb  other.  As  a  rule,  those  which 
contain  the  most  fusible  oxides  melt  the  most  readily,  and  the 
more  readily  in  proportion  as  the  base  is  in  excess.  Only  the 
alkaline  silicates  above  referred  to  are  soluble  in  water.  Most 
of  the  hydrous  silicates,  and  many  which  are  anhydrous  but 
contain  an  excess  of  base,  are  decomposed  by  acids;1  but  the 
anhydrous,  normal,  or  acid  silicates  are,  as  a  rule,  unaffected  by 
any  acid,  except  hydrofluoric,  although  they  can  be  rendered 
soluble  by  fusion  with  an  alkaline  carbonate.  When  the  fused 
mass  is  treated  with  HCl  -\-  Aq,  evaporated  to  dryness,  and 
again  digested  with  the  same  acid,  the  silica  remains  as  a  gritty 
insoluble  powder,  and  can  at  once  be  recognized.  The  pres- 
ence of  silica  in  a  mineral  can  generally  also  be  discovered  by 
fusing  a  small  fragment  before  the  blow-pipe  with  microcosmic 
salt.  This  decomposes  the  mineral,  but  does  not  dissolve  the 
silica,  which  is  left  floating  in  the  clear  bead. 

1  Soluble  compounds  of  the  basic  radicals  are  thus  formed,  while  the  silica 
separates  either  as  a  gelatinous  hydrate,  or  as  a  loose,  anhydrous  powder. 
Sometimes,  however,  the  silica  also  dissolves,  and  generally  it  is  taken  up  to 
a  limited  extent.  In  every  case  the  silica  becomes  anhydrous,  and  completely 
insoluble  if  the  solution  is  evaporated  to  dryness  at  the  boiling-point  of  water. 


448  SILICON.  [§399. 

399.  Constitution   of  Native  Silicates.  —  The    symbols   of 
many  of  the  native  silicates  have  already  been  given,  and  those 
of  others  will  be  discovered  by  solving  the  problems  which  fol- 
low this  division.    Moreover,  the  principles  on  which  these  sym- 
bols are  written  have  been  fully  developed.     There   is  still, 
however,  an  uncertainty  in  regard  to  the  constitution  of  some 
of  these  minerals,  and  it  is  not  always  possible  to  deduce  from 
the  results  of  analysis  a  probable  rational  formula,  even  when 
these  results  are  known  to  be  essentially  accurate.     This  uncer- 
tainty arises  from  several  causes  :  —  1.  We  have  no  sure  crite- 
rion of  the  purity  of  the  mineral,  since  we  are  not  able,  as  in 
the  case  of  artificial  products,  to  eliminate  admixtures  by  re- 
peated crystallizations  ;  2.  The  methods  commonly  used  to  de- 
termine the  molecular  weight  of  compounds  (66)  entirely  fail 
in  the  case  of  these  silicates,  and  this  important  element  for  fix- 
ing the  symbol  is  therefore  wanting1  (23).     Moreover,  when 
the  molecule  is  condensed  (that  is,  contains  several  atoms  of 
silicon)  unavoidable  inaccuracies  in  the  processes  may  vitiate 
conclusions  based  on  analysis  alone  ;  3.  The  constant  replace- 
ment of  one  radical  by  another  (214)  renders  the  composition 
of  most  silicates  very  complex,  and  we  are  frequently  at  a  loss 
to  determine  the  part  which  a  given  radical  may  play  in  the 
compound.     This  is  especially  true  of  hydrogen,  for  we  have 
no  certain  means  of  deciding  whether  the  atoms  of  this  element 
in  a  hydrous  silicate  are  a  part  of  the  molecule  itself,  or  only 
connected  with  it  in  the  water  of  crystallization. 

400.  Symbols  of  Native  Silicates.  —  The  composition  of  most 
native  silicates  may  be  so  varied  by  replacements,  without  any 
essential  change  in  external  qualities,  that  such  a  mineral  spe- 
cies cannot  be  distinguished  as  a  compound  of  definite  radicals, 
but  merely  as  conforming  to  a  certain  general  formula,  and  the 
only  specific  character  is  the  atomic  ratio  between  the  several 
composite  radicals  of  which  the  mineral  may  be  supposed  to 
consist  (214).     Thus  the  composition  of  common  Garnet  may 
in  general  be  represented  by  the  formula 

n     vi  iv 


1  We  have  reason  to  hope  that  a  more  accurate  knowledge  of  the  laws  which 
govern  the  molecular  volume  of  compounds  in  the  solid  condition  may  here- 
after supply  this  deficiency. 


§  400.]  SILICON.  449 

n  v* 

but  It  may  be  either  Ca,  Mg,  Fe,  Mn,  or  Or,  and  [#J  either 

[ Alt],  [Fe]to  or  [  O2],  and  garnets  have  been  analyzed  in  which 
these  several  radicals  are  mixed  together  in  every  conceivable 
way  consistent  with  the  general  formula,  to  which  they  all  con- 
form. This  formula,  however,  is  merely  the  expression  of  a  defi- 
nite ratio  between  the  atomicities  of  the  several  classes  of  radicals 
taken  as  a  whole,  and  in  the  last  analysis  this  ratio  is  itself  the 
specif  c  character.  Hence  the  great  importance  of  the  atomic 
ratio  in  mineralogy,  and  we  have  already  seen  how  easily  it 
can  be  calculated  when  the  symbol  of  the  mineral  is  given 
(Probs.  58  and  95,  pages  394  and  397).  On  the  other  hand, 
from  the  ratio  we  can  as  easily  construct  the  general  formula  of 
the  mineral.  Thus  in  the  case  of  garnet  the  ratio  between  the 
dyad,  hexad,  and  tetrad  radicals  is  6  :  6  :  12,  or  1  :  1  :  2,  which 
is  evidently  expressed  in  its  simplest  terms  by  the  symbol  above. 
In  works  on  mineralogy  the  atomic  ratio  is  given  for  each  of 
the  native  silicates,  and  in  any  case  this  ratio  is  easily  deduced 
from  the  results  of  analysis  by  simply  extending  the  method  for 
finding  the  symbol  of  a  body  whose  molecular  weight  is  un- 
known (page  43).  Having  obtained  the  several  quotients  which 
represent  the  relative  number  of  atoms  on  the  supposition  that 
the  molecular  weight  is  100,  we  next  multiply  each  of  these 
quotients  by  the  quantivalence  of  the  respective  radicals.  Last- 
ly, we  add  together  these  products  f6r  each  class  of  replacing 
radicals,  and  compare  the  several  sums  thus  obtained.  For  ex- 
ample, an  actual  analysis  of  the  Bohemian  Garnet  (Pyrope) 
gave  the  following  results:  — 

Si  19.30  or  Si03  41.35 

[Jt/2]  11.92  «  A1205  22.35 

Fe  7.73  «  FeO  9.94 

Mn  2.01  «  MnO  2.59 

Mg  9.00  «  MgO  15.00 

Ca  3.77  "  CaO  5.29 

Or  3.19  «  CrO  4.17 

0'  43.77                                                 

100.69  100.69 

Dividing  now  each  per  cent  by  the  atomic  weight  of  the  radical, 
and  multiplying  by  its  quantivalence,  we  obtain  the  following 
numbers :  — 

cc 


450  SILICON.  [§  400 

2.76 
1.31 


Si 

IAI;_ 

Fe 
Mn 

Ca 
Cr 

(19.30  -J-  28    )   X   4  =  2.76 
|  (11.92  -r-  54.8)   X   6  =  1.31 
(  7.73  -7-  56   )   X   2  =  0.27 
(  2.01  -T-  55   )   X   2  =  0.07 
(  9.00  -r-  24   )   X   2  =  0.75 
(  3.77  _^_  40    )   x  2  =  0.19 
(  3.19  -*-  52.2)   X   2  =  0.12 

1.40 
whence  we  deduce  the  ratio, 

1.40  :  1.31  :  2.76     or     1:1:2  nearly. 

This  ratio,  although  not  exact,  is  as  near  the  theory  as  we  can 
expect,  considering  the  material  and  methods  used,  and  is  as 
near  as  we  usually  obtain. 

There  is  an  uncertainty  in  the  results  of  all  calculations  of 
this  kind,  which  arises  from  the  fact  that  we  have  no  sure  guide 
in  selecting  the  radicals  to  be  grouped  together.  Although  it 
is  true  in  general  tkat  replacements  are  limited  to  radicals  of 
the  same  atomicity,  yet  most  mineralogists  admit  that  radicals 
of  the  form  [./yi  ma7  replace  37?=,  and  some  go  so  far  as  to 
reckon  a  part  of  the  Si  among  the  basic  radicals.  Hence  our 
results  are  to  a  certain  extent  arbitrary,  and  in  many  cases  give 
no  satisfactory  information  as  to  the  constitution  of  the  mineral 
analyzed;  but  by  deducing  the  atomic  ratio  according  to  the  rule 
just  given,  we  in  all  instances  reduce  the  results,  as  it  were,  to 
the  simplest  terms,  and  bring  them  into  a  form  in  which  they 
can  be  most  conveniently  compared  with  each  other. 

It  is  usual  in  works  on  mineralogy  to  present  the  results  of 
analysis  on  the  old  dualistic  plan,  as  if  the  mineral  were  formed 
by  the  union  of  various  basic  anhydrides  with  silicon.  Starting 
with  such  data  it  is  not,  however,  necessary  to  calculate  the  per 
cent  of  each  radical  in  the  assumed  anhydrides  before  applying 
the  above  rule,  because  obviously  by  dividing  the  per  cent  of 
each  anhydride  by  its  molecular  weight  we  shall  obtain  the  same 
quotients  as  before.  For  example,  in  the  analysis  garnet  cited 
above,  where  the  data  are  given  in  both  forms,  we  have 


Si  :  So2  =  19.30  :  41.35  or  19.30  -f-  28  ==  41.35  -f-  60, 

and  so  for  each  of  the  other  values. 

In  the  symbols  of  the  silicates  as  formerly  written  on  the  du- 


§402.]  SILICON.  451 

alistic  theory,  the  atoms  of  oxygen  were  necessarily  apportioned 
among  the  different  radicals  in  proportion  to  their  quantivalence, 
although  this  fundamental  distinction  between  them  was  itself 
overlooked.  Thus  the  general  symbol  of  garnet  would  be  writ- 
ten, dualistically, 


and  it  is  evident  that  the  number  of  oxygen  atoms  is  in  each 
case  a  measure  of  the  relative  atomicities  of  the  radicals  with 
which  they  are  associated.  Hence  the  atomic  ratio  might  also 
be  found  by  comparing  together  the  quantities  of  oxygen  which 
the  several  assumed  oxides  contain,  and  this  is  the  manner  in 
which  the  calculation  has  generally  been  made  hitherto.  Hence, 
also,  the  atomic  ratio  has  been  called  the  oxygen  ratio,  and  was 
long  used  in  mineralogy  before  its  true  meaning  was  understood. 
But  although  the  old  method  gives  the  same  results  as  the  new, 
it  is  not  in  harmony  with  our  modern  theories,  and  is  practically 
less  simple.  Moreover,  the  principle  is  far  more  general  than 
the  old  method  would  imply,  and  may  be  used  with  all  classes 
of  compounds  as  well  as  with  those  in  which  the  radicals  are 
cemented  together  by  oxygen.  Furthermore,  it  is  sometimes 
useful  to  compare  the  atomic  ratios  of  the  complex  radicals 
which  may  be  assumed  to  exist  in  different  minerals,  and  inter- 
esting relations  may  frequently  be  discovered  in  this  way  which 
the  old  method  would  entirely  overlook.  This  has  already  ap- 
peared in  solving  the  problems  under  aluminum,  and  requires 
no  further  illustration. 

401.  Silicic  Sulphide.    SiS.2.  —  When  the  vapor  of  OS2  is 
passed  over  a  mixture  of  silica  and  carbon  intensely  ignited, 
this  compound  is  deposited  in  the  colder  part  of  the  tube  in 
"long,  white,  silky,  flexible,  asbestiform  needles."     It  can  be 
volatilized  in  a  current  of  dry  gas  ;  but  in  contact  with  moist  air, 
or  when  heated  in  aqueous  vapor,  it  rapidly  decomposes,  the 
products  being  IH^  and  amorphous  silica,  the  latter  of  which 
retains  the  form  of  the  sulphide.      It  undergoes  a  similar  de- 
composition in  contact  with  liquid  water,  but  the  silica  formed 
dissolves  completely,  and  the  solution,  when  concentrated,  yields 
the  same  singular  vitreous  hydrate,  resembling  opal,  described 
above. 

402.  Silicic  Fluoride,  SiF^  is  a  colorless  gas  (Sp.  Gr.  =  52) 


452  SILICON.  [§  403. 

which  can  only  be  reduced  to  the  liquid  state  by  great  pressure 
and  cold.     It  is  easily  prepared  by  the  reaction 


-f 

[357] 


When  brought  in  contact  with  the  air  it  is  at  once  decomposed 
by  aqueous  vapor  and  forms  dense  fumes.  Passed  into  water 
it  is  absorbed  in  large  quantities,  and  the  products  are  silicic 
hydrate  and  hydro-silicic  fluoride. 


Aq).  [358] 

The  same  solution  can  also  be  obtained  by  dissolving  silica  in 
hydrofluoric  acid.  It  forms,  when  saturated,  a  very  sour,  fum- 
ing liquid,  which  evaporates  at  40°  in  a  platinum  vessel  without 
leaving  any  residue.  Hence  a  very  simple  way  of  testing  the 
purity  of  silica. 

The  solution  of  hydro-silicic  fluoride  acts  as  a  strong  acid. 
It  dissolves  iron  or  zinc  with  the  evolution  of  hydrogen,  and 
decomposes  many  metallic  oxides,  hydrates,  and  carbonates, 
forming  definite  salts.  It  is  therefore  frequently  called  silico- 
fluoric  acid  (H^SiF^  and  its  salts  are  named  silico-fluorides. 
The  potassium  salt,  KfSiF6,  and  the  barium  salt,  &a*SiF&  are 
both  sparingly  soluble  in  water,  and  may,  therefore,  be  readily 
obtained  by  precipitation.  Moreover,  since  the  corresponding 
sodium  and  strontium  salts  are  much  more  soluble,  this  reagent 
may  be  used  to  distinguish  potassium  from  sodium,  but  more 
especially  barium  from  strontium.  Several  of  the  silico-fluor- 
ides may  be  readily  crystallized. 

Ammonic  silico-fluoride  (NH^^SiF^  .  xff20, 

Cupric  silico-fluoride  CusSiF6  .  7ffzO, 

Manganous  silico-fluoride  Mn=SiF6  .  1H20. 

403.  Silicic  Chloride,  SiCl4,  is  formed  by  passing  a  current 
of  chlorine  gas  through  an  intimate  mixture  of  silica  and  car- 
bon heated  intensely  in  a  porcelain  tube. 


SiO2  -+  C2  +  2O1-O1  =  2O©  +  Si®]*      [359] 
It  is  a  colorless,  volatile  liquid  (Sp.  Gr.  1.52),  boiling  at  50°, 


§406.]  SILICON.  453 

and  is  decomposed  by  water  into  hydrochloric  acid  and  silicic 
hydrate.  0J).  (6»r.  of  vapor  5.94.  It  is  also  slowly  decomposed 
by  R,S. 

HCl  [360] 


The  new  product  is  a  colorless  liquid,  boiling  at  96°,  and  yield- 
ing a  vapor  whose  0jj.  (6>r.  =  5.78. 

When  the  vapor  of  SiCl^  is  passed  through  a  white-hot  por- 
celain tube  it  undergoes  a  partial  oxidation,  and  is  in  part  con- 
verted into  an  oxychloride, 


t  +  0  =  Si2OCl6  +  ©K91,  [361] 

the  oxygen  required  coming  from  the  glazing  of  the  tube.  This 
compound  is  also  a  colorless  fuming  liquid,  resembling  the  chlo- 
ride. It  boils  at  138°,  and  has  0p.  (®r.  =  10.05. 

404.  Silicic  Bromide,  SiBr±,  may  be  formed  in  a  similar 
way,  and  closely  resembles  the  chloridex  but  is  less  volatile, 
boiling  at  153°,  and  crystallizing  at  from  12°  to  15°.     Sp.  ©t. 
of  vapor  12.05.     The  compound  SiCl^I,  0p.  (0>r.  =  7.25,  is 
also  known. 

405.  Silicic  Iodide,  SiI4,  is  a  colorless  crystalline  solid,  melt- 
ing at  120°.5,  and  boiling  at  about  290°.     Sp.  (g)r.  of  vapor 
19.12.     It  crystallizes  in  regular  octahedrons,  and  is  obtained 
by  passing  iodine  vapor  in  a  stream  of  C02  over  ignited  silicon. 

406.  Silicic  Hydride.  Siff4.  —  One  of  the  silicic  ethers  (409), 
when  heated  with  sodium,  furnishes  this  remarkable  compound 
in  a  pure  condition. 


iSI^  [362] 

The  sodium  induces  the  chemical  change  by  its  mere  presence. 
The  composition  of  silicic  hydride  has  been  determined  by  the 
following  reaction  :  — 


(2K-0-H+  ff20  +  Ag)  = 

(KfOfSiO  +  Aq)  +  4SI-SL  [363] 

It  is  a  colorless  gas,  which  inflames  at  a  very  low  temperature 
(under  some  conditions  spontaneously),  and  yields  when  burnt 
silicic  anhydride  and  water. 


454 


SILICON. 


[§407. 


407.  Silicic  Hydrochloride,  SiHCl&,  is  a  colorless  inflamma- 
ble liquid,  obtained  by  passing  HGl  over  ignited  silicon.     It 
has  0n.  (6>r.  =  4.64,  and  may  be  regarded  as  the  chloride  of 
the  radical  (Siff)  =  Cl&  corresponding  to  chloroform  (CH)  =  Cl& 
among  the  compounds  of  carbon.     The  corresponding  bromine 
and  iodine  compounds  are  also  known.       When  mixed  with 
water  these  substances  are  decomposed,  and  a  voluminous  white 
powder  is  formed  which  has  been  called  leukon. 

2SiffOls  +  3H20  =  (SiOH)fO  +  QffOl.     [364] 

Leukon  dissolves  in  the  alkaline  hydrates  or  carbonates,  yield- 
ing an  alkaline  silicate  and  evolving  hydrogen.  It  also  decom- 
poses water,  and  acts  in  general  as  a  reducing  agent. 

408.  Silicic  Ethide,  Si(  <72#5)4,  and  Silicic  Methide,  Si(  CH3)4 
are  two  colorless  volatile  liquids,  prepared  by  heating  SiOl4 
with  zinc  ethide   and    zinc  methide  in   sealed   tubes.     They 
boil  respectively  at  30°  and   153°,  and  their  vapors  have  a 
0p.  (S>r«  of  3.08  and"  5. 13.     Also  another  compound  has  been 
described  whose  symbol  may  be  written  0=Si^(  C2ffs)& 

409.  Silicates  of  .the  Organic  Radicals  or  Silicic  Ethers. — 
A  large  number  of  these  compounds  have  been  prepared,  con- 
taining the  radicals  methyl,  ethyl,  and  amyl,  either  singly  or 
associated  in  different  combinations.      They  are  all  colorless 
volatile  liquids,  highly  combustible,  and  having  for  the  most 
part  an  ethereal  odor.       We  give  in  the  following  table  the 
symbols,  the  boiling-points,  and  the  vapor-densities  of  several 
of  the  most  interesting  ethers,  and  of  the  chlorhydrines  (349) 
derived  from  them. 


Sp.  Gr. 
of  Liquid. 


Boiling-point. 


Vapor-density. 


Obs. 


Calc. 


1.059 
1.195 
1.259 

1.144 

0.968 


121° -122° 

98° -103° 

82° -86° 
201°-202°.5 

165° -166° 


5.38 
5.58 
5.66 
5.66 
9.19 

7.32 


5.26 
5.42 
5.57 
5.73 

8.93 

7.27 


§  409.] 


SILICON. 


455 


Sp.  Gr. 
of  Liquid. 


1.048 
1.44 
1.291 
1.020 


1.004 
0.981 
0.915 
0.913 


Boiling-point. 


134° 
157° 
137° 
104° 


190° 

143° -146° 
155° -157° 
245° -250° 

280°  -  285° 


Vapor-density. 


Obs. 


7.05 

6.76 

6.38 

12.02 


6.18 


Calc. 


5.68 
6.81 
6.54 
6.22 
11.86 

7.69 

6.23 

6.72 

10.12 

11.57 


The  following  equations  illustrate  some  of  the  reactions  by 
which  these  compounds  have  been  prepared  :  — 


4C2ff5-0-ff+  SiClt  =  (C2H5)/0/Si  +  1HCL   [365] 
SiCl,  =  ±(C&)£OfS£CL   [366] 
SiCl,  =  ^(C^fOfSiClf     [367] 


3(C2H5)-0-ff+ 
§(CZH5}-0-H+  Si2OCl6  = 


[368] 

SffCL   [369] 
+6  HCl  [370] 


In  general,  these  reactions  may  be  obtained  by  simply  heat- 
ing together  the  several  factors,  enclosed  if  necessary  in  sealed 
tubes.  The  process  is  usually  complicated  by  accessory  changes, 
and  a  mixed  product  results,  which  must  be  purified  by  repeated 
fractional  distillation. 


456 


QUESTIONS  AND   PROBLEMS. 


Questions  and  Problems. 

1.  Compare  the  properties  of  silicon  in  its  different  conditions  with 
those  of  boron. 

2.  Make  a  table  illustrating  the  relations  of  the  possible  hydrates 
of  silicon. 

3.  Required  the  general  formula  of  the  following  mineral  species 
whose  atomic  ratios  are  given  in  the  table :  — 


Anorthite 

Sarcolite 

Epidote 

Vesuvianite 

Leucite 

Beryl 

lolite 

Oligoclase 

Natrolite 

Analcime 

Harmotome 

Stilbite 


VI 


H 


Formula  required. 


iii,Si-a06  .  5/7,0 


The  number  of  atoms  of  oxygen,  which  form  the  vinculum  in  each 
of  the  above  formulas,  is  always  necessarily  equal  to  the  total  atom- 
icity of  all  the'  basic  radicals,  and  as  many  atoms  of  oxygen  are  asso- 
ciated with  the  acid  radical  as  are  required  to  complete  the  molecule. 
The  last  evidently  serve  to  bind  together  the  atoms  of  silicon  when 
they  are  in  excess  over  the  number  required  to  neutralize  the  base 
(151).  The  precise  form  we  give  to  the  symbols  is  in  great  meas- 
ure arbitrary,  and  must  be  determined  from  many  circumstances, 
which  do  not  influence  the  results  of  analysis ;  and  the  great  advan- 
tage of  expressing  these  results  in  the  form  of  an  atomic  ratio  is  found 
in  the  fact  that  they  are  thus  reduced  to  the  simplest  terms,  and  ex- 
hibited independently  of  all  hypothesis,  leaving  each  student  to  con- 
struct the  formulae  according  to  his  own  theoretical  conceptions. 


QUESTIONS  AND  PROBLEMS. 


457 


4.  Represent  the  constitution  of  Anorthite,  Sarcolite,  and  Beryl 
by  graphic  symbols. 

5.  In  the  following  table  the  percentage  composition  of  a  number 
of  native  silicates  is  given  on  the  usual  plan,  as  if  they  were  composed 
of  basic  anhydrides  and  silica.     It  is  required  in  each  case  to  deduce 
the  atomic  ratio  and  construct  the  formula. 


Na20 

KaO 

LizO 

FeO 

CaO 

MgO 

A120S 

Fe203 

SiOz 

H2O 

Ratio. 

Wollastonite 

48.3 

51.7 

1:2 

Pyroxene 

8.0 

24.9 

13.4 

53.7 

1:2 

Spodumene 

6.4 

29.4 

64.2 

1:2 

Petal!  te 

1.2 

3.3 

17.8 

77.7 

1:4 

Forsterite 

57.14 

42.86 

1:1 

Iron-Garnet 

17.3 

12.4 

33.1 

37.2 

1:1:2 

Zoisite 

37.3 

22.8 

39.9 

1:2:3 

Ilvaite 

31.5  12.3 

23.4 

32.8 

3:2:5 

Sarcolite 

4.1 

33.4 

22.8 

39.7 

1:1:2 

Andesine 

6.53 

1.08 

5.77 

1.08 

24.28 

1.58 

59.60 

1:3:8 

Analcime 

14.1 

23.3 

54.4 

8.2 

1:3:8:2 

Heulandite 

9.2 

16.9 

59.1 

14.8 

1  :  3  :  12  :  5 

6.  It  was  formerly  supposed  that  the  symbol  of  silica  was 
corresponding  to  that  of  boric  acid,  JB203,  when  Si  =  21  and  O  =  16. 
What  facts  can  you  adduce  in  support  of  the  symbol  adopted  in  this 
book? 

7.  Deduce  the  atomic  weight  of  silicon  from  the  data  of  (409)  ac- 
cording to  the  principle  of  (19).     It  is  assumed  that  the  percentage 
composition  of  the  various  compounds  has  been  accurately  determined 
by  analysis. 

8.  Point  out  the  analogies  between  the  properties  of  silicic  fluoride 
and  chloride,  and  those  of  the  corresponding  compounds  of  boron. 

9.  Compare  the  chemical  qualities  of  silicon  with  those  of  the 
elements  immediately  preceding  it  in  our  classification.     To  which 
element  is  it  more  closely  allied  ? 

10.  Compare  the  chemical  qualities  of  silicon  with  those  of  carbon, 
and  illustrate  by  examples  the  analogies  between  those  elements. 

11.  Point  out  the  examples  of  chlorhydrines  in  the  table  of  (409). 

1 2.  Describe  and  illustrate  by  reactions  the  methods  by  which  the 
silicic  ethers  and  chlorhydrines  are  prepared. 


20 


458  CAKBON.  [§  410. 


Division  XXL 

410.  CARBON.   G=  12.  —  Tetrad.      One   of  the   most 
widely  diffused,  and  one  of  the  most  important  elements  in  the 
scheme  of  terrestrial  nature.     United  to  the  three  aeriform  ele- 
ments, oxygen,  hydrogen,  and  nitrogen,  it  forms  the  chief  solid 
substratum  of  all  organized  structures.     Combined  with  oxygen 
it  forms  the  carbonic  anhydride  of  the  atmosphere,  which  is  the 
food  of  the  whole  vegetable  world.     In  a  nearly  pure  condition, 
or  combined  with  hydrogen,  it  is  found  in  the  strata,  forming 
those  deposits  of  coal  and  petroleum  which  are  such  great  stores 
of  light,  heat,  and  motive  power  (64).     Lastly,  it  is  an  essential 
constituent  of  the  limestones  and  Dolomites,  which  constitute 
an  important  part  of  the  rocky  crust  of  the  globe  (279)  (312). 
The  elementary  substance  is  found  in  nature  in  three  very  dif- 
ferent conditions,  namely,  coal,  graphite,  and  diamond. 

411.  Coal.  —  All  organized  tissues,  and  many  other  carbo- 
naceous materials,  when  heated  without  free  access  of  air,  are 
charred ;  that  is,  the  volatile  ingredients  are  driven  off,  and  more 
or  less  of  the  carbon  is  left  behind  in  an  uncombined  condition. 
Common  charcoal,  animal  charcoal,  lamp-black,  ivory -black,  &c. 
are  all  artificial  products  of  this  kind,  and  mineral  coal  is  the 
charred  remains  of  the  rank  vegetation  of  an  early  geological 
epoch.     Since  carbon  is,  under  all  circumstances,  infusible  and 
non-volatile,  coal  frequently  retains  the  structure  of  the  organic 
tissue  from  which  it  was  derived,  and  this  element  may  therefore 
be  regarded  as  the  skeleton  of  all  organic  forms,  which  in  the 
process  of  growth  gather  around  this  solid  nucleus  the  elements 
of  air  and  water.      The  great  porosity  of  many  kinds  of  coal, 
which  results  from  its  organic  structure,  renders  it  a  powerful 
absorbent  both  of  aeriform  and  liquid  materials,  and  hence  the 
use  of  wood-charcoal  as  a  disinfecting,  and  of  bone-black  as  a 
decolorizing,  agent.     The  ready  combustibility  of  coal  is,  how- 
ever, the  most  characteristic  and  important,  as  it  is  the  most 
familiar,  quality  of  this  variety  of  carbon,  which  is  peculiarly 
adapted  for  its  all-important  uses  as  fuel,  not  only  on  account  of 
its  high  calorific  power,  but  also  because  it  retains  its  solid  con- 
dition at  the  highest  furnace  heat,  and  because  the  product  of 
its  combustion  is  an  invisible  innocuous  gas,  the  appropriate 


§  413.]  CARBON.  459 

food  of  the  plant.  In  its  more  porous  conditions  coal  is  a  non- 
conductor of  heat  and  electricity,  has  a  low  specific  gravity  and 
a  high  specific  heat,  both  varying,  however,  in  different  varieties 
between  quite  wide  limits. 

412.  Graphite  has  usually  a  foliated  structure,  and  is  found 
occasionally  in  small  six-sided  tables  belonging  to  the  third  sys- 
tem, but  it  is  also  met  with  in  compact  amorphous  masses.  From 
its  frequent  association  with  crystalline  minerals,  evidently  the 
products  of  aqueous  action,  we  naturally  infer  that  it  must  have 
been  formed  in  a  similar  way ;  but  the  nature  of  the  process  is 
not  understood.     Graphite  is  very  soft,  leaving  a  black  shining 
streak  on  paper,  and  has  a  Sp.  Gr.  =  1.209.     It  is  practically 
incombustible,  although  it  burns  slowly  in  an  oxyhydrogen  flame. 
It  has  a  metallic  lustre,  and,  since  it  also  conducts  electricity 
nearly  as  well  as  the  metals,  it  has  been  called  metallic  carbon. 

The  carbon  which  separates  from  some  varieties  of  cast-iron 
when  the  molten  metal  slowly  cools  is  in  the  condition  of  graph- 
ite, and  the  cavities  in  iron  slags  are  sometimes  lined  with  crys- 
talline plates  of  the  same  material.  Moreover,  when  coal  is 
intensely  heated  in  a  close  vessel,  it  acquires  the  characteristic 
lustre  and  conducting  power  of  the  same  mineral,  and  a  similar 
product  is  formed  in  the  iron  retorts  in  which  illuminating  gas 
is  manufactured.  Ordinary  coke  also  sometimes  approaches  the 
same  condition,  but  all  these  materials  are  very  hard,  and  thus 
differ  from  true  graphite. 

Graphite  may  be  obtained  in  a  state  of  minute  sub-division 
by  heating  with  strong  sulphuric  acid  the  coarsely  pulverized 
mineral,  previously  mixed  with  one  fourteenth  of  its  weight  of 
potassic  chlorate,  and,  after  washing  with  water  and  drying, 
igniting  the  residue.  If  this  process  is  many  times  repeated 
the  graphite  is  converted  into  a  yellow  crystalline  product  which 
has  been  called  graphitic  acid,  and  which  has  been  regarded  as 
a  peculiar  compound  of  the  graphitoidal  condition  of  carbon. 
Analysis  gives  the  symbol  Ouff405. 

413.  Diamond.  —  This  well-known  gem  is  also  a  crystalline 
condition  of  carbon.      It  affects  the  forms  of  the  monometric 
system,  and  may  be  cleaved  in  directions  which  are  parallel  to 
the  faces  of  the  regular  octahedron.     Its  peculiar  brilliancy  is 
due  to  a  very  high  refractive  and  dispersive  power  united  to  a 
strong  lustre  called  adamantine.    The  effect  is  greatly  increased 


460  CARBON.  [§413. 

by  the  lapidary,  who  cuts  numerous  facets  on  the  gem,  which 
reflect  and  disperse  the  light  in  various  directions.  Diamond 
is  the  hardest  substance  known,  and  can  therefore  only  be  cut 
with  its  own  powder.  Opaque  stones  called  "black  diamonds," 
which  are  otherwise  valueless,  are  pounded  up  and  used  for  this 
purpose.  On  account  of  its  great  hardness  the  diamond  is  also 
used  for  cutting  glass,  and  the  convex  faces  of  the  crystals  en- 
able them  to  bear  the  necessary  pressure  without  breaking. 
The  diamond  burns  at  a  high  temperature  much  more  readily 
than  graphite,  and  in  an  atmosphere  of  pure  oxygen  sustains  its 
own  combustion,  yielding  C02  like  all  other  forms  of  carbon. 
It  is  a  poor  conductor  of  electricity,  but  when  intensely  heated 
in  the  voltaic  arc  it  suddenly  acquires  this  power,  becomes  spe- 
cifically lighter,  and  is  converted  into  a  kind  of  coke.  The  dia- 
mond has  never  been  made  artificially,  and  we  have  no  knowl- 
edge as  to  its  origin.  It  is  found  in  alluvial  soil  at  only  a  few 
localities,  chiefly  in  India,  Borneo,  and  Brazil. 

It  will  tnus  be  seen  that  carbon  presents  the  most  remarkable 
example  of  allotropism  which  has  been  observed  in  nature,  and 
the  essential  differences  between  the  three  states  appear  chiefly 
in  the  form,  density,  and  capacity  for  heat,  which  we  sum  up  in 
the  table  below :  — 

Crystalline  Form.  Sp.  Gr.  Sp.  Heat. 

Wood  Charcoal  Amorphous  0.300  0.2415 

Graphite  Hexagonal  2.300  0.2027 

Diamond  Isometric  3.500  0.1469 

In  all  these  forms  carbon  is  chemically  the  same,  and  yields 
the  same  product  (  O02)  when  burnt.  It  is  not  only  non-vola- 
tile and  infusible,  but  does  not  even  soften  in  the  hottest  fire ; 
although  in  the  experiments  of  Despretz,  with  a  voltaic  battery 
of  intense  energy,  it  appears  to  have  undergone  incipient  fusion, 
and  to  have  been  partially  volatilized.  Lastly,  although  com- 
bustible at  a  high  temperature,  yet  under  ordinary  conditions 
carbon  effectually  resists,  and  for  an  indefinite  period,  the  action 
of  all  atmospheric  agents,  and  its  uses  for  fuel  on  the  one  hand, 
and  for  printing-ink  on  the  other,  are  remarkable  illustrations  of 
the  singular  twofold  aspects  of  this  element  hi  the  economy  of 
nature. 


§414]  CARBON  AND  OXYGEN.  461 


CARBON  AND   OXYGEN,  OR  SULPHUR. 

414.  Carbonic  Anhydride.  O02.  —  With  this  aeriform  pro- 
duct of  ordinary  combustion  the  student  must  have  already  be- 
come familiar.  Although  a  gas  under  ordinary  conditions,  it  can 
be  condensed  by  pressure  and  cold  to  a  colorless  limpid  liquid, 
which  freezes  by  its  own  evaporation  to  a  light  flocculent  solid, 
outwardly  resembling  snow,  a  condition  in  which  it  is  used  to 
produce  a  great  degree  of  cold.  As  a  gas  it  is  distinguished  by 
the  absence  of  all  those  qualities  which  affect  the  senses,  and 
hence,  although  playing  such  an  important  part  in  nature,  it  es- 
caped notice  until  the  year  1757,  when  it  was  first  discovered 
by  Dr.  Black.  It  is  not  only  a  product  of  the  combustion  of 
all  carbonaceous  materials,  and  of  the  slow  oxidation  of  organic 
tissues  called  decay,  but  it  is  also  one  of  the  chief  products  of 
respiration,  and  of  the  other  processes  of  animal  life.  Carbonic 
anhydride  is  likewise  formed  during  fermentation,  and  is  the 
cause  of  the  effervescence  in  all  fermented  liquids.  It  is  a  pro- 
duct of  volcanic  action,  and  is  copiously  evolved  from  the  earth 
in  many  localities,  especially  in  volcanic  districts.  As  it  is  much 
heavier  than  the  air,  0p.  (S)r.  =  1.529,  it  not  unfrequently  col- 
lects in  wells,  mines,  and  caverns,  and  it  is  the  choke-damp  which 
has  occasioned  so  many  serious  accidents ;  for,  although  not, 
properly  speaking,  poisonous,  the  free  secretion  of  carbonic  an- 
hydride from  the  body  is  an  essential  condition  of  life,  and  this 
is  arrested  as  soon  as  the  amount  in  the  atmosphere  exceeds  a 
few  per  cent.  Hence  also  the  necessity  of  ventilating  crowded 
apartments. 

Although  an  immense  flood  of  carbonic  anhydride  is  being 
constantly  poured  into  the  atmosphere  from  the  various  sources 
just  enumerated,  yet  in  the  beautiful  balance  of  creation  the 
plant  restores  the  equilibrium  which  these  causes  tend  to  dis- 
turb. This  product  of  animal  life,  of  decay,  and  of  combustion 
is  the  food  of  the  vegetable  world,  and,  as  has  been  stated  (64), 
the  sun's  rays  acting  on  the  leaves  of  the  plant  undo  the  work  of 
destruction,  and  while  the  plant  fixes  the  carbon  in  its  tissues, 
the  oxygen  is  restored  to  the  atmosphere.  While  the  plant  is 
an  apparatus  of  reduction,  the  animal  is  an  apparatus  of  com- 
bustion, in  which  the  carbon  it  receives  with  its  food  is  burnt 
in  each  act  of  life,  and  every  breath  carries  back  carbonic  an- 


462  CARBON  AND  OXYGEN.  [§415. 

hydride  to  the  atmosphere,  ready  to  be  reabsorbed  by  the  plant, 
and  repass  through  the  phases  of  organic  life. 

Water  dissolves  very  nearly  its  own  volume  of  carbonic 
anhydride  gas  (53),  and  this  important  agent  is  as  universally 
diffused  through  the  waters  of  the  globe  as  it  is  through  the 
atmosphere,  and  sustains  the  same  intimate  relations  to  the 
plants  and  animals  which  inhabit  the  water  as  it  does  to  those 
which  live  in  the  air.  Moreover,  in  this  condition  of  solution 
carbonic  anhydride  is  a  very  active  and  important  agent  in  the 
mineral  kingdom,  exerting  a  powerful  solvent  action  on  many 
minerals  which  would  be  otherwise  unaffected  by  water,  and 
thus  causing  extensive  geological  changes.  (279),  (312),  and 
Prob.  67,  page  394. 

Although  the  solution  of  O02  in  water  acts  in  all  respects 
like  a  simple  solution  (54),  yet  there  are  reasons  for  regarding 
it  as  a  solution  of  carbonic  acid,  and  writing  its  symbol  thus, 
(H2=02-O0  -f-  Aq).  It  has  an  acid  reaction  (39),  and  dissolves 
iron  with  the  evolution  of  hydrogen  gas  (335).  Moreover,  it 
neutralizes  many  basic  hydrates,  and  such  reactions  are  most 
simply  regarded  as  examples  of  direct  metathesis,  thus :  — 

(Ca=02=ff2  +  HfOfCO  +  Aq)  = 

Ca=02=CO  +  (2H20  +  Aq).  [371] 

Carbonic  acid  is  a  weak  dibasic  acid,  and  forms  two  distinct 
classes  of  salts,  the  most  important  of  which  have  already  been 
described  (123),  (124),  &c.,  and,  as  may  be  inferred  from  what 
has  been  said,  carbon  is  next  to  silicon  the  most  abundant  acid 
radical  in  the  mineral  kingdom. 

The  quantity  of  O02  formed  by  the  burning  of  a  known 
weight  of  carbon  can  be  collected  and  weighed  with  the  greatest 
accuracy,  and  it  was  thus  that  the  atomic  weight  of  carbon  was 
determined.  Dumas  found  in  a  series  of  very  accurate  experi- 
ments that  100  parts  of  pure  carbon  yield  exactly  366.66  +  parts 
of  C02. 

415.  Carbonic  Oxide,  CO,  is,  like  C02,  a  colorless  gas,  but 
contains  in  the  same  volume  only  one  half  as  much  oxygen,  and 
its  molecules  not  being  saturated,  act  as  powerful  dyad  radicals 
(69).  The  gas  is  devoid  of  odor  or  taste,  is  very  poisonous,  is 
but  slightly  soluble  in  water,  and  has  never  been  condensed  to 
the  liquid  state.  When  ignited  it  burns  with  a  blue  flame,  and 


§415.]  CARBON  AND  OXYGEN.  463 

when  in  contact  with  heated  metallic  oxides  it  acts  as  a  power- 
ful -reducing  agent,  in  each  case  eagerly  absorbing  more  oxygen 
without  changing  its  volume.  It  is  formed  abundantly  in  all 
furnaces  and  grates  whenever  the  first  product  of  combustion, 
always  O0.2,  subsequently  passes  through  a  mass  of  ignited  car- 
bonaceous combustible,  and  it  plays  an  important  part  in  many 
metallurgical  processes,  not  unfrequently  occasioning  a  great 
loss  of  heat  by  escaping  combustion.  It  is  also  formed  when 
steam  is  passed  over  ignited  coal,  and  it  is  a  chief  ingredient  in 
the  so-called  water  gas. 

Carbonic  oxide  may  be  obtained  in  a  pure  condition  by  a 
number  of  chemical  reactions,  of  which  the  following  is  the 
most  available  :  — 


Potassic  Ferrocyanide. 

Fe=OfSOa  +  2KfOfSOa  +  3(Nff4)2=02=S02  -f-  6(9®.  [S72] 

So,  also,  when  oxalic  acid  is  dehydrated,  —  best  by  heating  the 
crystals  with  concentrated  sulphuric  acid,  —  it  breaks  up  into 
C02  and  CO,  which  are  evolved  in  equal  volumes,  and  the  CO 
may  be  isolated  by  passing  the  gas  through  a  solution  of  caustic 
alkali  which  absorbs  the  C02. 


[373] 

In  theoretical  chemistry  CO  is  chiefly  interesting  as  an  im- 
portant acid  radical,  and  when  acting  in  this  capacity  it  is  usu- 
ally known  as  carbonyl.  It  is  the  acid  radical  not  only  in  the 
normal  carbonates,  but  also  in  almost  all  of  the  organic  acids. 
The  following  beautiful  synthetical  reaction,  obtained  by  simply 
heating  carbonic  oxide  gas  with  potassic  hydrate,  illustrates  the 
relations  of  this  radical  to  an  important  class  of  organic  acids. 

K-0-H  +  CO  =  K-O-(CO-H).  [374] 

Potassic  Formate. 

Under  the  influence  of  direct  sunlight,  carbonic  oxide  combines 
directly  with  chlorine,  forming  CO=C12,  called  phosgene  gas. 
This  compound  is  at  once  decomposed  both  by  water  and  am- 
monia (Nffz),  and  in  each  of  the  resulting  reactions  the  radical 
CO  evidently  retains  its  integrity. 


CO-  C12  +  H20  =  2ffCl  +  CO,.  .    [375] 

CO  -  Cl,  +  ±ffsN  =  H,,H.fNf  CO  +  2NH4  Cl.      [376] 

Urea. 


464  CARBON  AND  OXYGEN.  [§416. 

41  6.  Oxalic  Acid.  Hf  02=  C2  02  .  2ff2  0.  —  The  anhydride 
of  this  acid,  C203,  has  never  been  obtained,  and  the  acid  itself 
forms  the  first  term  of  an  important  series  of  compounds,  all  of 
which  contain  hydrogen.  Strictly,  therefore,  it  cannot  be  classed 
with  the  simple  compounds  of  carbon  and  oxygen,  but  neverthe- 
less it  is  best  studied  in  this  connection. 

The  calcic  and  potassic  salts  of  oxalic  acid  are  found  in  the 
juices  of  many  plants,  and  when  organic  bodies  are  oxidized  by 
nitric  acid  or  similar  agents,  this  acid  is  one  of  the  most  com- 
mon products.  It  is  made  in  the  arts  by  the  action  of  nitric 
acid  on  sugar  or  starch,  and  also  by  heating  sawdust  with  caustic 
potash. 

Oxalic  acid  easily  crystallizes  in  prisms  which  have  the  com- 
position indicated  above.  These  crystals  lose  their  water  of 
crystallization  at  100°,  and  at  160°  the  body  itself  is  broken 
up,  the  products  being  carbonic  anhydride  and  formic  acid  ; 
but  the  greater  part  of  the  last  is  still  further  decomposed  into 
water  and  carbonic  oxide,  and  a  portion  of  the  oxalic  acid  al- 
ways sublimes  unchanged. 

C2ff20,  =  Cff202  +  C02  and  Cff202  =  H20  +  CO.   [377] 

When,  however,  the  acid  is  heated  with  glycerine,  the  reaction 
is  arrested  at  the  first  stage,  and  yields  the  equivalent  quantity 
of  formic  acid. 

Oxalic  acid  is  both  diatomic  and  dibasic.     Thus  we  have 

Normal  Potassic  Oxalate  X2=02=C202.    H.20, 

Acid  Potassic  Oxalate  (  Salt  of  Sorrel)  .  H,K~-  02=  C2  02  .  H2  0, 
Super-acid  Potassic  Oxalate  ff,K=OfC202  .  JffOfC202  .  2H20. 

The  last  is  usually  regarded  as  a  molecular  compound.  With 
the  exception  of  the  alkaline  salts,  the  oxalates  are,  as  a  rule, 
insoluble  or  difficultly  soluble  in  water,  and  on  the  great  insolu- 
bility of  calcic  oxalate  several  important  analytical  processes 
depend. 

Calcic  oxalate,  when  heated,  is  converted  into  calcic  car- 
bonate. 

Ca*OfC202  =  Ca-OfGO  +  CO.  [378] 

When,  however,  the  acid  itself  is  heated  with  an  excess  of  lime, 
we  obtain  a  somewhat  different  result. 


-ff.   [379] 


§416.]  CARBON  AND  OXYGEN.  465 

Oxidizing  agents  convert  oxalic  acid  into  C02  (Prob.  18, 
page  391)  by  removing  the  typical  hydrogen. 

HfOfCiOt  +0  =  ffzO  +  2C02.  [380] 

Substances  having  a  strong  attraction  for  water  transform 
the  acid  into  <702  and  CO  [373]. 

Argentic  oxalate,  when  heated,  is  resolved  with  explosion 
into  metallic  silver  and  OOZ. 

AfffOfCiO,  =  Aff-Aff  +  2  (70,  [381] 

On  the  other  hand,  when  an  amalgam  of  pota?sium  is  heated 
in  an  atmosphere  of  (702,  the  gas  is  absorbed  and  potassic  ox- 
alate results. 

K-K  +  2C02  =  Kf  02=  C2  02.  [382] 


These  reactions  all  justify  the  rational  symbol  assigned  to  ox- 
alic acid,  and  by  writing  the  symbol  as  in  the  mar- 
gin the  relation  of  the  atoms  is  made  more  evident.  H-0-&0 
We  thus  see  that  dry  oxalic  acid  may  be  regarded  H-O-frO 
as  formed  by  the  union  of  two  atoms  of  the  com- 
pound radical  (ffo-CO);  held  together  by  one  affinity  of  each 
of  the  carbon  radicals,  which,  when  not  thus  satisfied,  may  join 
the  radical  to  any  other  group  of  atoms  that  is  in  the  condition 
to  hold  it.  This  radical  is  called  oxatyl,  and  dry  oxalic  acid  is 
evidently  the  corresponding  radical  substance.  Oxatyl,  as  is 
evident,  is  not  only  univalent,  but  also  monobasic,  and  therefore 
must  transform  any  group  of  atoms  to  which  it  is  united  into 
an  acid.  Moreover,  the  basicity  of  such  an  acid  will  be  meas- 
ured by  the  number  of  atoms  of  oxatyl  which  it  contains.  Now 
nearly  all  the  so-called  organic  acids  may  be  regarded  as  com- 
pounds of  oxatyl  with  the  different  hydrocarbon  radicals. 
Those  containing  one  atom  of  oxatyl  are  monobasic,  those  con- 
taining two  atoms  are  dibasic,  those  containing  three  are  triba- 
sic.  Oxatyl,  however,  must  itself  be  regarded  as  a  compound 
of  carbouyl  with  hydroxl,  and  thus  we  arrive  at  this  important 
general  principle.  The  basicity  of  an  organic  acid  is  determined 
by  the  number  of  atoms  of  Ho  which  it  contains  associated  with 
carbonyl.1  Moreover,  it  now  appears  why  the  basicity  may  be 

1  This  theory  of  the  constitution  of  organic  acid,  which  has  been  recently 
advanced  and  abundantly  illustrated  by  Professor  Frankland,  of  London,  is-one 
20*  DD 


466  CABBON  AND  NITROGEN.  [§417. 

less  than  the  atomicity;  for  the  last  is  measured  by  the  total 
number  of  Ho  atoms  present,  however  united  to  the  nucleus  of 
the  compound  (43).  But  while  the  hydrogen  of  all  the  Ho 
atoms  in  a  compound  may  be  displaced  by  very  positive  met- 
als, or  compound  radicals  of  either  class,  we  can  only  displace 
by  double  decomposition  with  bases  the  hydrogen  of  those  atoms 
which  are  associated  with  carbonyl. 

The  explanation  of  this  important  principle  seems  to  be  that, 
while  a  strong  positive  metal,  such  as  sodium,  will,  like  a  pow- 
erful magnetic  pole,  increase  the  attraction  of  the  point  of  affin- 
ity to  which  it  is  opposed,  and  thus  give  to  it  an  energy  it 
would  not  otherwise  possess,  yet  in  the  ordinary  metathetical 
reactions  the  atoms  of  hydrogen  cannot  be  displaced  unless  they 
are  in  a  polar  condition,  such  as  is  determined  by  their  associ- 
ation with  carbonyl. 

417.  Carbonic  Sulphide.  CS2.  —  Charcoal  burns  in  an  at- 
mosphere of  sulphur  vapor  with  almost  as  much  energy  as  in 
oxygen,  forming  a  colorless  gas,  which  at  the  ordinary  temper- 
ature of  the  air  condenses  to  a  very  volatile  liquid,  distinguished 
for  its  very  great  refractive  and  dispersive  power,  and  much 
used  in  the  arts  as  a  solvent  of  phosphorus,  sulphur,  and  caout- 
chouc. The  compound  CS  has  never  been  obtained  in  a  free 
state,  but  the  following  reactions  indicate  that  it  exists  as  an 
acid  radical  in  certain  sulphur  salts  (38). 

K^S  +  CS,  =  KfSf  CS.  [383] 

(Pb=02=(N02)2  +  ZfSfCS  +  Aq)  = 

(2K-0-N02  +  Aq).  [384] 


=  PbS+  (H2=S2=CS+Aq).  [385] 


CARBON  AND   NITROGEN. 

418.  Cyanogen.  CN.  —  Although  carbon  will  not  combine 
directly  with  nitrogen,  yet  when  heated  in  an  atmosphere  of 
this  gas,  and  in  the  presence  of  a  strong  alkaline  base,  the  two 
elements  unite  with  the  alkaline  metals,  and  the  resulting  pro- 
of the  most  important  contributions  recently  made  to  Chemistry,  and  the  au- 
thor would  here  acknowledge  his  great  indebtedness  to  the  papers  of  this  emi- 
nent chemist  in  the  preparation  of  the  present  division  of  this  work. 


§419.]  CARBON  AND  NITROGEN.  467 

duct  contains  the  compound  radical  GN,  with  which  the  stu- 
dent is  already  familiar,  under  the  name  of  cyanogen. 

KfOfCO-\-±C+N*N=  2K-CN+  SCO.     [386] 

Like  carbouyl,  cyanogen  is  a  very  strong  negative  or  acid 
radical,  and,  if  we  accept  the  theory  of  Frankland,  we  need  admit 
no  other  acid  radical  than  these  two  "  in  investigating  the  whole 
range  of  organic  compounds."  *  In  many  of  its  chemical  relations 
cyanogen  closely  resembles  the  elements  of  the  chlorine  group, 
forming  many  compounds  which  are  analogous  to  the  corre- 
sponding chlorides,  bromides,  and  iodides,  but  in  other  respects 
it  differs  widely  from  these  elements,  both  on  account  of  its 
compound  nature,  and  the  singularly  complex  relations  of  the 
two  elements  of  which  it  consists.  Its  univalent  condition  is 
an  obvious  result  of  the  atomicities  of  its  two  constituents. 

419.  Cyanogen  Gas,  CN-CN  or  Cy-Cy,  bears  the  same  re- 
lation to  the  radical  GN  that  chlorine  gas  bears  to  the  element 
chlorine  (69),  (113).  It  is  easily  made  by  heating  mercuric 
cyanide. 

[387] 


At  the  same  time  a  brown  non-volatile  product  is  formed  which 
is  called  paracyanogen.  This  body  is  isomeric  with  the  gas, 
but  probably  represents  a  more  condensed  molecular  condition, 
and  is  converted  wholly  into  cyanogen  when  heated  in  an  inert 
atmosphere. 

Cyanogen  has  been  condensed  to  a  liquid,  boiling  at  —  20°.7, 
and  freezing  below  —  34°,  which  is  its  melting-point.  The  gas 
is  colorless,  has  a  suffocating  odor,  and  is  poisonous.  It  burns 
with  a  beautiful  flame,  which  recalls  the  color  of  peach-blossoms, 
and  the  products  of  its  combustion  are  C02  and  W^N".  It  dis- 
solves in  water,  but  not  so  freely  as  in  alcohol.  The  aqueous  so- 
lution, moreover,  is  not  permanent,  for  the  cyanogen  slowly  unites 
with  the  elements  of  water,  changing  into  ammonic  oxalate. 

CN-  CN  +  4ff2  0  =  (NH^f  Of  C2  0*          [388] 

1  There  is,  however,  a  class  of  somewhat  obscure  acids,  formed  by  the  action 
of  H2=03=S02  on  various  organic  substances,  in  which  the  radical  (Ho-S0z)- 
appears  to  play  the  same  part  as  the  radical  oxatyl  in  the  compounds  just  no- 
ticed. Such  bodies  were  formerly  said  to  be  copulated  er  conjugated,  and 
these  terms,  though  latterly  discarded,  were  not  wholly  inappropriate. 


468  CAKBON  AND  NITROGEN.  [§420. 

On  the  other  hand,  when  ammonic  oxalate  is  heated  the  action 
is  reversed,  and  these  facts  show  how  easily  carbonyl  and  cyan- 
ogen are  convertible.  Cyanogen  unites  directly  with  potassium, 
forming  K-CN. 

420.  Hydrocyanic  Acid.  H-CN.  —  The  anhydrous  acid  (a 
combustible  and  very  volatile  liquid)  is  most  readily  obtained 
by  passing  H.2S  over  Hg  Gy2,  but  a  solution  of  the  acid  in  water 
(the  prussic  acid  of  pharmacy)  may  be  made  by  distilling  po- 
tassic  cyanide  or  ferro-cyanide  with  dilute  sulphuric  acid. 

Hydrocyanic  acid  has  the  peculiar  odor  of  bitter  almonds, 
and  is  intensely  poisonous.  It  is  a  very  unstable  body,  and 
both  the  hydrous  and  the  anhydrous  acid  undergo  spontaneous 
decomposition,  which  is  greatly  accelerated  by  the  action  of  the 
light.  When  diluted  with  water,  and  mixed  with  a  mineral 
acid,  it  is  more  permanent,  but  it  is  so  volatile  that  even  the 
very  dilute  acid  used  in  pharmacy  rapidly  loses  strength  when 
exposed  to  the  air. 

By  absorption  of  the  elements  of  water  both  ammonic  oxalate 
and  ammonic  formate  are  slowly  formed  in  the  aqueous  acid. 
The  first  by  a  reaction  similar  to  [388],  and  the  second  thus, 

H-  GN  +  2H20  =  Nff4-  0-(  OO-ff).          [389] 


Ammonic  Formate. 


When  the  vapor  of  ammonic  formate  is  passed  through  a  red- 
hot  tube,  the  last  reaction  is  reversed.  In  like  manner,  when 
hydrocyanic  acid  is  mixed  with  hydrochloric  acid  (both  concen- 
trated), we  have 


H-  GN  +  HGl  +  2ff20  =  H-0-(  OO-ff  )  +  Nff<  Gl.  [390] 

Formic  Acid. 

421.  Cyanides.  —  Hydrocyanic  acid  reddens  litmus  feebly, 
and  potassic  cyanide  has  an  alkaline  reaction  (39).  It  however 
freely  dissolves  Hg  0,  forming  Hg  Gy&  and  in  a  similar  way  (or 
more  readily  by  metathesis  from  potassic  cyanide)  a  large  num- 
ber of  metallic  cyanides  may  be  obtained.  The  alkaline  cyan- 
ides are  very  soluble  in  water,  and  several  of  the  cyanides  of 
the  heavier  metals,  like  Hg  Cy^  dissolve  to  a  limited  extent. 
Most  of  them,  however,  are  insoluble  in  pure  water,  but  with 
few  exceptions  they  all  dissolve  freely  in  solutions  of  the  alka- 
line cyanides,  with  which  they  form  double  salts,  and  solutions 
of  Ag  Gy  and  Au  Gy  in  (KCy  +  Aq)  are  very  much  used  in 


§422.]  CARBON  AND  NITROGEN.  469 

the  process  of  electroplating.  The  double  cyanides  are  a  still 
more  definite  and  numerous  class  of  salts  than  the  simple  cyan- 
ides. Among  them  we  may  cite  as  examples 

Ag  Cy  .  KCy        and         Zn  Cy2  .  2  KCy. 

All  these  cyanides  contain  cyanogen  as  such,  and,  with  few 
exceptions,  when  heated  with  dilute  hydrochloric  acid,  they 
yield  HCy,  and,  if  soluble,  are  violent  poisons.  There  is,  how- 
ever, another  class  of  compounds  formed  by  combining  with  the 
alkaline  cyanides  the  cyanides  of  iron,  cobalt,  chromium,  pla- 
tinum, and  a  few  of  the  rarer  metals,  which  do  not  evolve 
HCy  under  the  influence  of  hydrochloric  acid,  and  have  not  the 
same  deadly  character.  Moreover,  the  metals  which  they  con- 
tain cannot  be  displaced  by  the  usual  metathetical  methods. 
Hence  we  have  come  to  the  conclusion  that  these  bodies  are  not 
simple  cyanides  of  the  metals,  but  contain  far  more  complex 
radicals,  of  which  the  metals  just  mentioned  form  a  part.  The 
most  important  of  these  compounds  are  described  in  the  next 
two  sections. 

422.  Ferrocyanides.  R^(FeC6N&}  or  RfCfy.  —  Potassic 
ferrocyanide  (yellow  prussiate  of  potash),  KfCfy,  is  an  impor- 
tant commercial  product,  manufactured  on  a  large  scale  by  fus- 
ing nitrogenized  animal  matter  with  potassic  carbonate  and  iron- 
filings,  lixiviating  the  resulting  mass  with  water,  and  crystalliz- 
ing. The  salt  forms  large  yellow,  square,  tabular  crystals,  is 
very  much  used  in  dyeing,  and  is  the  primary  source  of  all  the 
cyanogen  compounds.  It  may  also  be  made  from  KCy  or  HCy 
by  the  following  reactions  :  — 


FeS  +  SK-CN—  K^FeC^)  +  K^S.        [391] 

.  [392] 


Prussian  Blue. 

-ffo  +  Ag)  = 
2lFe,JHos  +  (SKfCfy  +  Aq).  [393] 

When  fused,  the  ferrocyanide  is  partially  decomposed,  yield- 
ing potassic  cyanide,  which  is  made  in  great  quantities  .in  this 

=  \K-  GN  +  Fe  Q  +N-N.       [394] 


470  CARBON  AND  NITROGEN.  [§423. 

way.  By  previously  mixing  the  ferrocyanide  with  potassic 
carbonate  a  larger  product  is  obtained,  but  less  pure,  as  potassic 
cyanate  is  formed  at  the  same  time. 


e  +  COr  [395] 

From  the  solution  of  the  potassium  salt  various  ferrocyanides 
are  easily  prepared  by  simple  metathesis,  and  several  of  them 
have  striking  and  characteristic  colors.  Thus,  when  the  solu- 
tion is  mixed  with  hydrochloric  acid  and  ether,  hydro-ferrocy- 
anic  acid  is  precipitated. 


Ofy  +  ±HCl  =  Hf  Cfy  +  ±KCL  •         [396] 
c  salt  we  obtain  Pr 

C76  +  ZK^Cfy  +  Aq)  = 


With  a  ferric  salt  we  obtain  Prussian  blue  (ferric  ferrocy- 
anide). 


(12JTCT  +  Aq).  [397] 


Hence  the  origin  of  the  name  cyanogen  (KVUVOS 

With  a  ferrous  salt  the  precipitate  is  white  or  nearly  so,  but 
becomes  blue  in  contact  with  the  air. 

(Fe-Cl,  +  KfCfy  +  Aq)  =  K2,Fe=Cfy  +  (2KCI  +  Aq). 

[398] 
30-0  =  ^Fe^Cfys  +  SKfCfy  +  2Fe20&. 


Blue 

With  cupric  salts  we  have  a  red  precipitate. 


Cuz=Cfy  +  (2K2=OfS02  +  Aq).  [399] 

The  soluble  ferrocyanides,  as  a  rule,  crystallize  readily,  and 
the  crystals  usually  contain  several  molecules  of  water,  thus:  — 


Na^Cfy  .  12HZ0,         Na,K^Cfy  .  6H20,  Ba=Cfy  . 

KvBa=Cfy.    8fitd,  Zn=Cfy  .  3HZ0, 


423.  Ferricyanides.  —  By  passing  Cl-  Cl  through  a  solution 
of  K^Cfy  a  compound  is  formed,  K^\_Cfy2~],  containing  the 
hexad  radical  (Cfy-Cfy)l,  which  sustains  the  same  relation  to 


[§424.  CARBON  AND  NITROGEN.  471 

Ofy  that  Tfe  bears  to  [  7Y2]I.  On  evaporating  the  solution  we 
obtain  the  salt  in  deep-red  crystals,  which  are  an  article  of 
commerce  under  the  name  of  red  prussiate  of  potash. 


+  Aq).  [400] 

Other  ferricyanides  may  be  obtained  from  the  potassium  salts 
by  metathesis. 


With  a  solution  of  potassic  ferricyanide  ferrous  salts  give  a 
deep-blue  precipitate  called  Turnbull's  blue. 


+  (SJTCT  +  Aq).  [401] 

Ferric  salts,  on  the  other  hand,  give  no  precipitate,  and  it 
will  be  noticed  that,  while  these  salts  give.  a  blue  precipitate 
with  the  ferrocyanides,  the  ferrous  salts  give  a  blue  precipitate 
only  with  the  ferricyanides.  Hence,  a  simple  means  of  distin- 
guishing the  two  classes  of  salt. 

424.  Other  Compounds  of  Cyanogen.  —  Chlorine  forms  with 
cyanogen  three  polymeric  compounds. 


Cy-Cl  (Sp.  Gr.  30.7),  (%)=.f^  (SP-  Gr'  6L5)> 


In  like  manner  there  are  three  polymeric  oxygen  acids. 


ff-O-Qy, 

Cyanic  Acid.  Dicyanic  Acid.  Cyanuric  Acid. 

The  tendency  to  polymerism  (70),  here  manifested,  is  a  re- 
markable feature  of  the  cyanogen  compounds,  and  gives  rise  to 
products  of  great  complexity,  most  of  which,  however,  have  been 
but  little  studied.  Their  condensed  molecules  are  evidently 
held  together  by  complex  radicals  formed  by  the  coalescing  of 
several  atoms  of  cyanogen,  and  it  is  evident  that  the  atomicity 
of  such  radicals  must  be  equal  to  the  number  of  elementary  atoms 
of  any  one  kind,  nitrogen  or  carbon,  of  which  they  consist.  On 
the  same  principle  the  constitution  of  the  ferro-  and  ferri-cyan- 
ides,  as.  well  as  that  of  paracyanogen,  may  be  explained. 


472  CARBON  AND  NITROGEN.  [§425. 

425.  Cyanates.  —  Cyanic  acid,  referred  to  above,  forms  an 
important  class  of  salts  which  have  a  great  theoretical  interest 
on  account  of  the  remarkable  transformations  of  which  many  of 
them  are  susceptible.  Potassic  cyanate  is  readily  prepared  by 
dropping  litharge  into  the  fused  cyanide,  or  ferrocyanide,  so 
long  as  the  oxide  is  reduced. 


KCy  +  PbO  =  K-0-Cy  +  Pb.  [402] 

In  order  to  crystallize  the  salt  the  fused  mass  should  be  ex- 
hausted with  alcohol  of  80%,  since  on  evaporating  an  aqueous 
solution  the  salt  is  slowly  decomposed.  The  same  change  takes 
place  rapidly  when  the  salt  is  heated  with  potassic  hydrate. 


K-0-GN+K-O-H+HtO^KfOfCO  +  NB*  [403] 

When  potassic  cyanate  is  mixed  in  solution  with  ammonic 
sulphate  a  metathesis  takes  place,  but  the  resulting  ammonic 
cyanate  is  at  once  transformed  into  a  remarkable  compound- 
ammonia  or  amine  (167)  called  urea, 

NHi  0-GN—  H^HfNf  CO,  [404] 

and  by  this  reaction  the  synthesis  of  this  complex  organic  pro- 
duct was  first  obtained. 

The  most  interesting  of  the  cyanates  are  the  compounds  called 
cyanic  ethers,  in  which  methyl,  ethyl,  &c.  are  the  basic  radicals. 
They  are  easily  obtained, 


K-  0-  Gy  +  K,  G,Hf  02=S02  =  K2=  Of  SO,  +  O2ff5-  0-  Cy,  [405] 

Distilled  together. 

and  the  investigation  of  the  many  wonderful  transformations  of 
which  they  are  susceptible  was  one  of  the  most  important  steps 
in  the  progress  of  organic  chemistry. 

As  cyanic  acid  when  heated  with  an  excess  of  potash  yields 
ammonia,  so  these  cyanic  ethers  yield  various  amines. 


H-0-CN+  2K-0-ff=  KfOfCO 

[406] 
-  0-GN+  2K-  0-ff=  K2=  02=  GO  +  H,H,  C2H^N. 

Ethylamine. 

The  following  reactions  are  equally  instructive  :  — 
O2H5-  0-CN+2K-0-  C2ff5  =  Kf  Of  CO+(O,  ffJfN.  [407] 


Triethvlamine. 


§427.]  CARBON  AND  HYDROGEN.  473 

C02.  [408] 


ff-0-C2ff30  = 
Acetic  Acid. 


Ethylacetamide. 

2,(C2ff5)/N2=CO  +  (70^  T409] 

Diethylcarbamide. 

The  above  reactions  will  appear  more  simple  if  the  symbols 
of  the  cyanic  ethers  are  written  after  the  ammonia  type  thus, 
OfffytGO'^  and  that  this  is  their  true  constitution  is  rendered 
probable  by  the  fact  that  a  body  has  recently  been  discovered 
called  cyanetholine,  which  appears  to  be  a  true  cyanic  ether. 
It  is  made  by  the  reaction 

Na-0-CzH5+  CyCl  =  NaCl  +  C2ff5-0-Cy;  [410] 

and  when  acted  upon  by  potash  it  yields,  not  ethylamine,  but 
common  alcohol.     (Prob.  3,  page  77.) 

426.  Sulpho-cyanates.  —  By  fusing  potassic  cyanide  with 
sulphur  we  obtain  the  sulphur  salt  corresponding  to  potassic 
cyanate,  or  K~S~  Cy,  and  from  this,  as  from  the  cyanate,  a  large 
number  of  compounds  may  be  derived.  Potassic  sulpho-cyan- 
ate,  although  without  action  on  the  ferrous  compounds,  strikes 
a  deep-red  color  in  a  solution  which  contains  the  least  trace  of 
a  ferric  salt,  and  for  this  reason  is  a  very  useful  reagent. 


CARBON  AND   HYDROGEN. 

427.  "Organic  Chemistry." — It  has  already  been  stated  that 
organized  beings  consist  of  materials  composed  chiefly  of  carbon, 
hydrogen,  oxygen,  and  nitrogen ;  but  few  as  are  the  chemical 
elements  concerned  in  the  processes  of  organic  life,  nevertheless 
the  number  of  compounds  which  have  been  discovered  in  the 
tissues  of  animals  and  plants,  or  formed  by  their  chemical  met- 
amorphosis, is  exceedingly  great.  Such  compounds  are  called 
Organic  Compounds,  and  in  works  on  chemistry  they  are  usually 
studied  together  under  the  separate  head  of  Organic  Chemistry. 

While  the  molecules  of  mineral  compounds  consist  for  the 
most  part  of  only  a  few  atoms,  those  of  organic  compounds  fre- 
quently contain  a  very  large  number,  and  the  diversity  in  or- 
ganic chemistry  is  obtained,  not  by  multiplying  the  number  of 
elements,  but  by  varying  the  molecular  grouping.  It  was  for- 


474  CARBON  AND  HYDROGEN.         [§428. 

merly  supposed  that  the  great  complexity  thus  produced  was 
sustained  by  what  was  called  the  vital  principle ;  but  although 
the  cause  which  determines  the  growth  of  organized  beings  is 
still  a  perfect  mystery,  we  now  know  that  the  materials  of  which 
they  consist  are  subject  to  the  same  laws  as  mineral  matter,  and 
the  complexity  may  be  traced  to  a  peculiar  quality  of  carbon 
already  described.1  The  atoms  of  carbon  are  prone  to  combine 
among  themselves,  and  the  same  tendency  which  appears  in 
several  of  the  elements  to  a  limited  extent  is  developed  in  the 
case  of  carbon  to  a  very  high  degree.  Carbon  is  the  skeleton 
of  an  organic  compound  in  a  peculiar  sense.  Its  atoms,  locked 
together  like  so  many  vertebrae,  form  the  framework  to  which 
the  other  elements  are  fastened,  and  thus  a  complex  molecular 
structure  is  rendered  in  a  wonderful  measure  compact  and  stable. 

Organic  chemistry  is  simply  the  chemistry  of  the  compounds 
of  carbon,  and  has  no  distinctive  character  except  that  which 
the  peculiar  qualities  of  this  singular  element  give.  More- 
over, although  in  a  compendium  of  the  science  it  may  be  con- 
venient, or  even  necessary,  to  distinguish  between  mineral  and 
organic  chemistry  on  account  of  the  great  preponderance  and 
importance  of  the  compounds  of  carbon  ;  yet  in  a  work  on  Chem- 
ical Philosophy,  where  the  object  is  not  to  enumerate  facts, 
there  seems  to  be  no  good  reason  for  departing,  in  the  case  of 
this  single  element,  from  the  general  scheme,  or  treating  it 
more  fully  than  is  required  to  illustrate  the  new  and  important 
principles  which  it  presents  to  our  notice.  Indeed,  in  an  ele- 
mentary work  no  other  course  is  possible,  since  a  mere  list  of 
the  known  compounds  of  carbon  would  fill  a  large  volume. 

428.  Hydrocarbons.  —  If  we  conceive  that  the  carbon  atoms 
of  the  successive  molecules  are  held  together  by  the  smallest 
possible  number  of  bonds,  then,  as  shown  in  (34),  the  symbols 
of  the  possible  hydrocarbon  compounds  of  this  class  would  be 
expressed  by  the  general  symbol j7M^+2,  and  each  number  of 
the  series  would  differ  from  the  preceding  by  CH2.  Again,  if 
we  conceive  that  the  skeleton  of  carbon  atoms,  instead  of  pre- 
senting at  either  end  an  open  affinity  as  in  Fig.  a,  forms  a 
closed  chain  as  in  Fig.  b,  the  hydrocarbon  atoms  of  this  second 
class  would  be  expressed  by  CnH^  and  form  another  series  with 
a  constant  difference  as  before  of  Cff2.  Lastly,  if  we  start  with 
l  The  student  should  very  carefully  review  (34)  in  this  connection. 


§428.]  CARBON  AND  HYDROGEN.  475 

a  nucleus  of  carbon  atoms  grouped  together  as  in  Fig.  c,  form- 
Fig,  a.  Fig.  b.  Fig.  c. 

'  #  s  (7  =  (7 

=  <?  tf- 

-C-C-C-C-C-O-          •  .  -C  <7- 

......          =0r  GS 

*  c  -  *•*•<* 

II 

ing  the  hydrocarbon  C&HQ,  and  add  to  this  successive  incre- 
ments of  CH2,  we  obtain  still  a  third  series  of  hydrocarbons 
expressed  by  the  symbol  Cnff2n_6, 

Each  of  the  above  symbols  represents  a  series  of  actual  com- 
pounds, of  which  many  members  are  known,  as  shown  in  the 
table  on  page  477.  Moreover,  the  hydrocarbons  of  any  one 
series  all  sustain  the  same  general  relations  to  chemical  reagents, 
undergo  similar  changes  when  exposed  to  the  same  influences, 
and  present  a  regular  gradation  in  their  physical  properties  cor- 
responding to  the  change  in  their  composition.  Compounds  so 
related  are  said  to  be  homologues^  and  such  a  series  is  called  an 
homologous  series. 

Obviously,  however,  the  three  series,  whose  relations  have 
been  just  described,  do  not  include  all  the  possible  hydrocarbons, 
for,  starting  with  any  one  of  the  more  complex  molecules  of  the 
first  class,  in  which  the  carbon  atoms  are  united  by  the  smallest 
possible  number  of  bonds,  we  may  assume  that  the  open  bonds 
are  successively  closed  two  by  two  by  the  more  intimate  union  of 
the  carbon  atoms  among  themselves,  and  we  shall  thus  obtain  a 
derived  series,  whose  successive  members  differ  by  the  quantity 
ff2.  The  general  symbol  of  such  a  series  would  be  C7B^B_TO)  +  2i 
the  first  term  being  Cnff2n+2,  m  standing  for  the  number  of 
the  required  term  counting  from  the  first.  Compounds  thu3 
related  are  termed  isologues,  and  it  is  obvious  that  those  hydro- 
carbons in  the  three  series  of  homologues  exhibited  above, 
which  contain  the  same  number  of  carbon  atoms,  are  members 
of  the  same  series  of  isologues ;  but  it  is  also  obvious  that  be- 
sides these  three  an  indefinite  number  of  parallel  homologous 
series  are  theoretically  possible.  The  student  will  best  under- 
stand the  relations  of  this  scheme  by  tabulating  the  possible 
compounds,  arranging  the  homologues  in  parallel  columns  with 
the  isologues  on  the  same  horizontal  line.  He  will  thus  see 


476  CARBON  AND  HYDROGEN.         [§428. 

that  there  is  no  limit  to  the  number  of  hydrocarbons,  except 
that  fixed  by  the  instability  of  the  resulting  molecules. 

A  table,  prepared  as  just  directed,  would  not,  however,  ex- 
hibit all  the  possibilities  in  this  scheme  of  the  hydrocarbons, 
since  we  may  conceive  of  the  atoms  of  each  of  the  more  com- 
plex compounds  as  arranged  in  different  ways,  and  thus  giving 
rise  to  one  or  more  isomeric  modifications.  For  example,  we 
may  construct  the  symbol  of  the  hydrocarbon  C4If10  as  indicated 
by  either  of  the  rational  formulae  (C~  G-  C-  C>  ff10  or  &(  CH^H, 
and  with  a  little  ingenuity  the  student  will  readily  discover  in 
any  case  the  number  of  such  commutations  possible,  only  he 
must  carefully  distinguish  between  a  mere  arbitrary  change  in 
the  relative  position  of  the  atoms  and  a  fundamental  difference 
of  arrangement.  The  last  alone  implies  a  difference  of  quali- 
ties in  the  substance  which  the  formulae  represent,  and  indicates 
the  possibility  of  isomeric  modifications.  Review  in  this  con- 
nection (70). 

It  must  not  be  supposed  that  all  the  hydrocarbons  which  our 
theory  prefigures  are  actually  possible,  that  is,  represent  com- 
pounds which  either  have  been  or  may  be  isolated ;  for  as  yet 
the  theory  has  taken  into  account  but  one  condition,  namely,  the 
atom-fixing  power  of  carbon,  and  many  causes  may  intervene 
to  render  unstable  the  compounds  which  are,  from  this  one  point 
of  view,  theoretically  possible.  As  the  number  of  carbon  atoms 
increases,  a  condition  is  soon  reached,  when,  if  we  may  so  ex- 
press it,  the  molecule  cannot  sustain  its  own  weight,  and  in  all 
cases  the  atoms  must  be  so  grouped  as  to  preserve  certain  polar 
relations  between  its  several  parts.  As  yet,  however,  we  do 
not  understand  the  laws  which  determine  molecular  stability, 
and  cannot,  therefore,  foresee  the  result  in  a  given  case,  so  that 
we  are  unable  to  control  our  algebraic  method.  Still,  with  all 
this  uncertainty  the  theory  has  its  value,  and  not  only  serves 
for  the  time  to  classify  our  facts,  but  gives  us  one  of  those 
glimpses  of  the  order  of  creation  which  are  the  greatest  privi- 
lege that  the  student  of  nature  enjoys. 

But  with  all  the  limitations  which  the  conditions  of  stability 
impose,  the  number  of  possible  hydrocarbons  must  be  very  large, 
and  the  compounds  actually  known  can  form  but  a  very  small 
portion  of  those  which  may  hereafter  be  isolated.  The  series  of 
homologues  given  on  page  477  include  the  greater  part  as  well 


§428.] 


CARBON  AXD  HYDROGEN. 


477 


as  the  most  important  of  the  known  compounds  of  this  class. 
Of  other  series  a  few  members  here  and  there  have  been  recog- 
nized, but  in  regard  to  most  of  these  our  knowledge  is  imperfect 
and  uncertain.  Many  hydrocarbons  are  found  in  a  free  state 
in  nature,  but  mixed  together  in  the  petroleums,  and  in  those 
combustible  gases  like  the  fire-damps  of  coal-mines  which  are 
evolved  from  the  earth  in  many  localities.  Others  are  found 
among  the  products  of  the  dry  distillation  of  coal,  wood,  or  other 
organic  tissues,  and  in  either  case  the  individual  compounds  are 
isolated  by  various  processes  of  fractional  distillation.  Others, 
again,  have  been  obtained  by  various  chemical  reactions,  and 
of  these  a  few  of  the  more  characteristic  are  given  below :  — 


Marsh  Gas  Series. 

Acetylt 

CnHtn  +  Z. 

B.  P. 

( 

Methylic  Hydride            CHt 

Acetylene 

Ethylic  Hydride              CZHQ 

Allylene 

Propylic  Hydride            CZHS 

Crotonylene 

Butylic  Hydride              CtHw 

o°.o 

Valerylene 

Amy  lie  Hydride               C5HIZ 

30°.2 

Allyl? 

Hexylic  Hydride              CGHlt 

61°.3 

Heptylic  Hydride            CjHw 

90°.4: 

Octylic  Hydride               C8H19 

119°.5 

Nonylic  Hydride              CQH20 

150°.8 

Olefiant  Gas  Series. 

Es 

sen 

QA. 

B.  P. 

Ethylene                       <72JFT4 
Propylene                     C3H9 

—  17°.8 

Oil  of  Turpentine 

Butylene                       CtH8 

-f35°.0 

Amylene                        CB^IO 

56°.0 

Hexylene                       C6H13 

39°.0 

Heptylene                     C,Hlt 

55°.0 

Octylene                        ^8-^ia 

95°.0 

pi 

Nonylene                      £9-^18 

125°.0 

fi> 

em 

Decatylene                    ^10-^20 

174°.9 

C* 

Endecatylene                C^Hy^ 

195°.8 

°n 

Dodecatylene                ^12^21 

216°.2 

Benzol 

Tridecatylene                ^13^26 

235° 

Toluol 

Cetene                           ClGIf3a 

Xylol 

Cerotene  (parafflne)     C21HM 

270° 

Cumol 

Melene                          Qo^eso 

375° 

Cymol 

n"2»-6 
C7H8 


B.  P. 


111° 

129° 
148° 
175° 


Several  of  the  terms  in  the  above  series  are  represented  by 
at  least  two  isomeric  compounds.  Thus  we  find  in  the  Penn- 
sylvania petroleums,  mixed  with  the  last  six  members  of  the 
marsh  gas  series,  five  other  hydrocarbons,  C^o  to  CBff^  iden- 


478  CARBON  AND  HYDROGEN.         [§429. 

tical  in  composition,  but  having  boiling-points  uniformly  eight 
degrees  higher.  The  common  difference  between  these  boiling- 
points  (which  have  been  determined  with  great  accuracy)  is 
very  nearly  30°,  and  it  is  probable  that  a  similar  constancy 
would  appear  in  all  series  of  truly  homologous  compounds,  and 
the  discrepancies  noticeable  in  several  members  of  the  series  as 
above  exhibited  are  probably  to  be  referred  to  the  fact  that 
bodies  are  here  included  which  do  not  belong  to  the  same  type. 
429.  Marsh  Gas  Series.  CnH^+^  —  Molecules  having  this 
composition  must  necessarily  be  closed  and  saturated.  Hence 
the  hydrocarbons  of  this  class  are  indifferent  bodies,  but  they 
readily  yield  substitution  compounds  containing  chlorine  and 
bromine.  Thus,  when  we  act  on  marsh  gas  (  Cff4)  with  chlo- 
rine, hydrochloric  acid  is  formed,  and  we  obtain  either  CH3Cl, 
CHCI&  (7(7/4,  or  (7,  the  products  of  the  reaction  varying  with 
the  conditions  of  the  experiment  and  the  proportions  of  the  fac- 
tors. Marsh  gas  may  be  obtained  perfectly  pure  from  zinc 
methide  (324),  which  is  decomposed  by  water,  as  shown  by  the 
following  reaction  :  — 


2ff20  =  Zn-OfH^  +  2Off4.      [411] 

By  a  similar  reaction  ethylic  and  amylic  hydrides  can  be  ob- 
tained from  zinc  ethide  and  zinc  amylide. 

The  first  member  of  the  series  has  long  been  known  as  a 
product  of  the  decomposition  of  vegetable  tissue  under  water, 
and  hence  the  trivial  name  Marsh  Gas.  It  is  the  chief  constit- 
uent of  the  fire-damp  of  coal-mines,  and  of  common  illuminating 
gas  obtained  by  the  dry  distillation  of  coal.  It  is  most  conven- 
iently prepared  by  heating  potassic  acetate  with  a  large  excess 
of  potassic  hydrate  mixed  with  quicklime. 


K-0-C2H&0  +  K-  0-ff=  KfOfCO  +  OJH.  [412]  - 

It  can  also  be  obtained  by  either  of  the  following  reactions,  but 
they  have  only  a  theoretical  interest. 


[413] 

CffCl3  +  Bff-ff=  3HCI  +  Cff4.  [414] 

4Cn  =  4CuS  +  OH34.     [415] 


§430.]  CARBON  AND  HYDROGEN.  479 

The  first  two  reactions  are  obtained  by  reducing  carbonic  chlo- 
ride or  chloroform  with  nascent  hydrogen,  the  last  by  passing 
JI2S  gas  mixed  with  CS2  vapor  over  ignited  copper. 

Marsh  gas  has  no  sensible  qualities,  and  has  never  been  lique- 
fied. Like  the  other  members  of  the  series  it  is  highly  combus- 
tible, and  burns  with  a  luminous  flame. 

Marsh  gas  and  its  homologues  may  be  regarded  as  hydrides 
of  radicals  having  the  general  form  C^/^i+u  and  we  are  al- 
ready acquainted  with  many  compounds  in  which  these  atomic 
groups  manifest  a  marked  individuality.  Ethylic  iodide  is  easily 
prepared,  and  by  acting  on  this  compound  with  zinc  we  obtain 
a  hydrocarbon  which  may  be  regarded  as  the  corresponding 
radical  substance. 

2C2ffa-I+  Zn  ==  Znl,  +  C2ff5-C2ff5.  [416] 

In  like  manner  similar  products  may  be  obtained  with  several 
of  the  homologous  compounds,  and  by  using  iodides  of  two  radi- 
cals simultaneously  the  so-called  double  or  mixed  radicals  may 
be  produced. 


Zn  =  Znl*  +  CHZ-C,H5.     [417] 

These  hydrocarbons,  however,  are  all  isomeric,  if  not  identical, 
with  the  normal  terms  of  the  marsh  gas  series. 

430.  Olefiant  Gas  Series.  CnH^  —  Molecules  of  this  type 
are  not  necessarily  closed,  but  are  capable  of  fixing  two  addi- 
tional monad  atoms,  and  of  acting  as  dyad  radicals.  The  first 
member  of  the  series  was  discovered  by  an  association  of  Dutch 
chemists  in  1795,  who,  noticing  its  characteristic  property  of 
combining  directly  with  chlorine,  called  it  Olefiant  (oil  making) 
Gas,  because  the  product  of  this  union  is  a  thick  flowing  liquid. 
This  product,  long  known  as  the  Oil  of  the  Dutch  chemists,  is 
ethyleue  chloride,  C2H±C12.  Ethylene  bromide  and  ethylene 
iodide  may  be  formed  in  a  similar  way,  and  the  tendency  to 
form  compounds  of  this  type  distinguishes  this  class  of  hydro- 
carbons, which  are  called,  for  this  reason,  olefines.  Moreover, 
the  hydrogen  atoms  of  the  bivalent  radical  may  all  be  replaced 
by  chlorine  or  bromine,  and  the  resulting  compound  still  retain 
the  same  typical  character.  This  is  shown  by  the  following 
reactions  :  — 

+  Br-Br  =  (  Cf^-Br^  [418] 


480  CARBON  AND  HYDROGEN.  [§431. 

(C2fft)=Br2  +  K-0-H=  C2ff3Br  +  KBr  +  HZ0,  [419] 

C2ff3Br  +  Br-Br  =  (  C2ffBBr)=Br»  [420] 

(O2ff3Br)=Br2  +  K-0-H=  C2ff2Br2  +  KBr  +  ff20,  [421] 

which  may  be  repeated  with  the  successive  products,  until  at 
last  we  obtain  02Br4  and  (  O2Br4)=Br2  as  the  final  results. 

Olefiant  gas  is  most  readily  obtained  by  heating  alcohol  with 
several  times  its  volume  of  strong  sulphuric  acid.  The  reaction 
is  somewhat  complicated,  but  the  result  is  a  dehydration  of  the 
alcohol,  and  the  same  effect  may  be  produced  with  zincic 
chloride  (323). 

O2ff60  —  ff20  =  O2ff4.  [422] 

Like  marsh  gas  this  aeriform  hydrocarbon  has  no  sensible 
qualities  save  a  slight  odor,  due  probably  to  a  trace  of  ether. 
It  has,  however,  been  liquefied,  and  is  slightly  soluble  in  water. 
Containing  twice  as  much  carbon  in  the  same  volume,  it  burns 
with  a  more  luminous  flame  than  the  lighter  gas,  and  the  illumi- 
nating power  of  coal-gas  is  due  in  no  inconsiderable  measure  to 
its  presence.  Olefiant  gas  combines  directly,  not  only  with 
chlorine,  bromine,  &c.,  but  also  with  the  hydrogen  acids. 

02H,  +  ffl=  C2HJ.  [423] 

Moreover,  it  unites  with  hypochlorous  acid,  forming  a  chlor- 
hydrine. 

o,  Cl.  [424] 


These  reactions  of  olefiant  gas  illustrate  in  general  the  chemi- 
cal relations  of  this  series  of  hydrocarbons  ;  but  it  is  probable 
that  several  of  those  included  in  the  list  on  page  477,  although 
isomeric  with  terms  of  the  series,  are  really  formed  after  a  dif- 
ferent type.  A  large  number  of  them  are  only  known  as  con- 
stituents of  petroleum  or  products  of  dry  distillation,  and  have 
not  been  prepared  by  any  intelligible  process. 

431.  Acetylene  Series.  Cnff2n_2,  Acetylene.  —  This  gas  is 
formed  by  the  direct  union  of  its  elements,  when  the  current 
from  a  powerful  voltaic  battery  passes  between  carbon  poles  in 
an  atmosphere  of  hydrogen.  It  may  also  be  obtained  by  the 
action  of  water  on  potassic  carbide. 

=  2K-0-H+  O2ff2.  [425] 


§433.]  CARBON  AND  HYDROGEN.  481 

It  is  not  unfrequently  a  product  of  the  incomplete  combustion 
of  bodies  containing  carbon  and  hydrogen,  and  it  may  also  be 
prepared  in  other  ways.  Acetylene  acts  as  a  dyad  or  tetrad 
radical,  combining  with  nascent  hydrogen  to  form  C2Jf4  (ethy- 
lene),  with  bromine  to  form  G.2H2Br.2  or  C>2H.2Br^  and  with  hy- 
drobromic  acid  to  form  O2HBBr  or  O2ff4Br2.  It  is  not  yet  de- 
termined whether  these  bodies  are  identical  with  the  isomeric 
compounds  of  the  defiant  gas  series.  When  the  gas  is  passed 
through  a  solution  of  cuprous  chloride  in  ammonia,  a  highly 
explosive  compound  is  formed  as  a  red  precipitate,  which  has 
the  composition  (C.2H\_Cii^\)fO,  and  acts  as  a  basic  anhydride. 
The  other  hydrocarbons  of  the  series  have  similar  chemical  re- 
lations, but  have  not  been  thoroughly  studied. 

432.  Allyl.  —  When  allylic  iodide  is  digested  with  sodium 
and  distilled,  we  obtain  a  hydrocarbon  which  has  the  composi- 
tion 


Na-Na  +  2(C3ff5)-I=  2Na~I  +  C3ff5-O3ff5.      [426] 

This  product,  moreover,  unites  directly  with  one  or  two  mole- 
cules either  of  Br-Br  or  ff-I,  and  in  general  its  chemical  rela- 
tions are  those  of  a  homologue  of  acetylene.  But,  as  the  above 
reaction  indicates,  it  may  also  be  regarded  as  the  radical  sub- 
stance (22)  corresponding  to  allyl,  and  this  view  is  sustained 
by  the  fact  that  there  is  an  isomeric  hydrocarbon  having  similar 
chemical  relations,  but  different  physical  qualities,  which  is. 
more  probably  the  fifth  member  of  the  acetylene  series. 

433.  Essential  Oik.  CnH%n_^  —  Oil  of  Turpentine  and  many 
other  essential  oils  have  a  composition  represented  by  the  sym- 
bol 6i0^6,  and  there  are  a  few  others  which,  although  also  iso- 
meric, must  be  represented  by  a  multiple  of  this  symbol  ;  but 
no  other  members  of  the  series  are  known.  Oil  of  turpentine 
combines  l^)th  with  the  hydrogen  acids  and  with  water,  forming 
compounds  in  which  (  Owffl6)  acts  either  as  a  dyad  or  a  tetrad 
radical,  and  others  in  which  the  double  molecule  acts  as  a  hexad. 
radical.  Thus  we  have 


Exposed  to  the  air  oil  of  turpentine  absorbs  oxygen,  yieldipg  a 
resinous  product,  and  the  same  is  true  to  a  greater  or  less  de- 
gree of  the  other  essential  oils.     They  all  appear  to  have  simi- 
21  EE 


482  CARBON  AND  HYDROGEN.  [§434. 

lar  chemical  relations,  and  are  singularly  susceptible  of  allo- 
tropic  conditions  ;  but  on  what  the  differences  between  these 
isomeric  bodies  depend  we  are  as  yet  ignorant. 

434.  Phenyl  Series.  Cnff2n_&.  —  The  hydrocarbons  of  this 
class  are  found  in  coal-tar  and  Rangoon  petroleum,  and  are  iso- 
lated by  fractional  distillation.  Benzol,  or  benzine,  is  very 
much  used  in  the  arts,  but  the  commercial  product  is  more  or 
less  mixed  with  the  associated  hydrocarbons.  When  pure, 
benzol  becomes  solid  at  a  low  temperature,  melting  only  at  5°.5. 
Benzol  may  be  obtained  artificially  by  heating  benzoic  or 
phthalic  acid  with  an  excess  of  lime. 


CaO=: 

Benzoic  Acid.  Benzol. 

[427] 
Osff,04  +  2CaO  =  20aOOB  +  C6ff6. 

Phthalic  Acid.  Benzol. 

Benzol,  when  treated  with  chlorine  or  bromine,  yields  a  num- 
ber of  substitution  products.  By  the  action  of  nitric  acid  we 
obtain  (31) 

Nitro-benzol 
Dinitro-benzol 


and  when  acted  on  by  reducing  agents  (as  zinc  and  hydrochloric 
acid,  sulphuretted  hydrogen,  &c.),  nitro-benzol  is  converted  into 
aniline  (167),  and  thus  becomes  the  source  of  the  aniline  dyes. 

06fT5(N02)  +  3ff2S  =  C&H&(NH,)  +  2ff20  +  S3.  [428] 

The  other  hydrocarbons  of  this  series  may  be  regarded  as 
containing  the  same  group  of  carbon  atoms  as  benzol,  and  as 
derived  from  it  by  replacing  one  or  more  of  its  hydrogen  atoms 
with  the  radicals  methyl,  ethyl,  or  amyl.  It  is  evident  that  by 
replacing  several  atoms  of  hydrogen  with  methyl  we  -should  ob- 
tain a  body  of  the  same  composition  as  by  replacing  a  single 
atom  with  a  radical  richer  in  carbon,  and  we  have  abundant 
evidence  that  compounds  thus  obtained,  though  isomeric,  are 
not  identical. 

The  radical  CQH6,  called  Phenyl,  appears  to  be  the  nucleus  of 
all  the  hydrocarbons  of  this  series.  By  acting  on  boiling  benzol 
with  bromine,  we  obtain  the  bromide  of  this  radical, 

+  Br-Br  =  C,H5-Br  +  H-Br,  [429] 


§435.]  CARBON  AND  HYDROGEN.  483 

and  when  this  product  is  treated  with  sodium  a  hydrocarbon  is 
formed  which  is  regarded  as  the  corresponding  radical  substance. 

2  O6ff6-Br  +  Na-Na  =  C6H6-C6ff&  +  2NaBr.     [430] 

Benzol  is  then  phenylic  hydride,  and  its  homologues  are  hy- 
drides of  more  complex  radicals,  which  may  be  designated  as 
methyl-phenyl,  dimethyl-phenyl,  &c.  Besides  the  hydrocarbons 
included  in  the  five  series  just  described  we  know  also  a  few 
others.  Of  these  the  best  studied  are  phenylene,  (7c/4  and 
cinnamene,  Csff8,  corresponding  to  the  symbol  Onff2n_8,  and 
napthaline,  Cloff8,  corresponding  to  Cnff2n_i2.  They  all  com- 
bine with  chlorine  and  bromine,  and  have  in  general  the  chem- 
ical relations  of  artiad  radicals.  The  last  of  these  especially 
yields  with  these  elements,  besides  the  direct  compounds,  a  very 
large  number  of  substitution  products,  and  the  careful  investiga- 
tion of  these  bodies  by  Laurent  was  an  important  step  in  the 
progress  of  chemistry  (31). 

435.  Hydrocarbon  .Radicals.  —  It  is  evident  from  the  prin- 
ciples developed  in  (22)  and  (28),  and  still  further  illustrated 
in  (34),  that,  by  eliminating  successive  atoms  of  hydrogen, 
each  of  the  possible  hydrocarbons  of  the  scheme  exhibited 
above  may  yield  a  series  of  compound  radicals,  and  that  the 
atomicity  of  such  radicals  is  equal  in  any  case  to  the  number 
of  hydrogen  atoms  thus  lost. 

Such  of  these  radicals  as  contain  an  even  number  of  hydro- 
gen atoms  are  necessarily  artiads,  and  isomeric  with  either  ac- 
tual or  possible  hydrocarbons.  Moreover,  it  follows  from  (428) 
that  we  may  have  several  artiad  radicals  isomeric  with  each  of 
the  more  complex  compounds.  Thus  we  may  have  two  radicals 
((72^)=  and  (C2ff2)=  isomeric  with  acetylene,  and  the  same  is 
true  of  each  of  the  homologues  of  this  hydrocarbon.  Indeed, 
parallel  to  each  series  of  hydrocarbons,  except  the  first,  we  may 
have  one  or  more  series  of  artiad  radicals  isomeric,  term  by 
term,  with  the  normal  compounds,  and  the  number  of  possible 
isomers  in  any  case  is  the  same  as  the  number  of  the  series  in 
the  order  of  isologues  (428).  It  is,  however,  an  open  question 
whether  such  hydrocarbons  as  ethylene  or  acetylene  are  essen- 
tially different  from  the  radicals  of  the  same  composition  (69), 
and  we  do  not  distinguish  the  radicals  by  separate  names. 

The  hydrocarbon  radicals  which  contain  an  odd  number  of 
hydrogen  atoms  are  necessarily  perissads,  and  cannot,  without 


484  CARBON  AND  HYDROGEN.          [§43G. 

reduplication,  exist  in  a  free  state  [416],  [417],  and  [426]. 
Nevertheless,  the  radicals  homologous  with  methyl  and  phenyl 
play  such  an  important  part  in  numberless  chemical  reactions, 
and  preserve  their  integrity  through  so  many  changes,  that,  al- 
though only  known  in  combination,  their  individuality  is  as  well 
marked  as  that  of  the  elements  themselves.  Hence  it  is  with 
reason  that  they  have  received  distinctive  names.  With  most 
of  these  the  student  is  already  familiar,  but  to  those  previously 
noticed  we  may  here  add  Vinyl,  C2H3-,  Glyceryl,  Csfff  (the 
trivalent  condition  of  allyl),  and  the  radical  of  chloroform,  CN=, 
which  are  all  important  perissads. 

436  Oxygenated  Radicals.  —  Unless  associated  with  some 
very  powerful  basic  radical,  like  the  alkaline  metals,  the  simple 
hydrocarbons  always  form  basic  or  positive  radicals  (40).  To 
every  such  radical,  however,  corresponds  an  acid  or  negative 
radical  having  the  same  atomicity,  which  is  generated  by  re- 
placing a  portion  of  the  hydrogen  with  oxygen  (34).  Thus  :  — 

Methyl  Cff3  yields  Formyl       OHO  or  CO-H, 

Ethyl  C2ff5  "      Acetyl         C2ff30  «  C0-Cffs, 

Propyl  C3ff7  «      Propionyl    O3ff50  «  C0-C.2ff5, 

Butyl  C4ff9  "      Butyryl       O^H70  «  CO-C3JT7, 

Amyl  C5ffn          «      Valeryl        O5HQ0 

t 

Allyl  03ff5          «      Acryl          C3ff30 

Ethylene  C2X  yields  Glycolyl  CO-C  Hz  and  Carbonyl  (C0)3 
Propylene  CaH6    "      Lactyl      CO-C2H,  "    Malonyl    (CO)=C  H» 
Acetylene  C4#8    "      Acetonyl  CO-C3HQ  «    Succinyl 


If  the  theory  of  (41  6)  is  correct,  it  is  evident  that  the  virtue 
of  these  oxygenated  radicals  depends  entirely  on  the  number  of 
atoms  of  carbonyl  which  are  generated  in  the  hydrocarbon 
radical,  and  we  find  that  only  those  atoms  of  hydrogen  can  be 
replaced  which  are  so  related  to  the  molecule  that  the  atoms  of 
carbonyl  thus  formed  may  have  an  open  bond,  and  by  the 
addition  of  Ho  be  converted  into  oxatyl.  Hence  the  number 
of  oxygen  atoms  which  can  thus  be  introduced  into  the  radical 
can  never  exceed  its  atomicity,  and  the  basicity  of  the  acids, 
formed  by  the  union  of  the  resulting  negative  radicals  with  ffo, 
is  equal  to  the  number  of  oxygen  atoms  which  any  such  nega- 
tive radical  contains. 


§438.]   MONATOMIC  COMPOUNDS. — MARSH  GAS  SERIES.    485 


ALCOHOLS   AND  THEIR   DERIVATIVES. 

437.  Definition.  —  The  name  of  alcohol  is  applied  to  a  class 
of  bodies  which  resemble  common  vinic  alcohol  chiefly  in  that 
under  like  conditions  they  are  susceptible  of  similar  reactions. 
They  are  produced  in  a  variety  of  processes,  especially  by  fer- 
mentation ;  but  the  reactions  cannot  usually  be  traced.     They 
may  be  regarded  as  hydrates  of  the  hydrocarbon  radicals  (40), 
or  as  formed  from  the  hydrocarbons  themselves  by  replacing 
one  or  more  atoms  of  hydrogen  with  hydroxyl,  and  their  atom- 
icity (43)  depends  on  the  number  of  atoms  of  Ho  thus  intro- 
duced into  the  molecule.     Hence  we  have  monatomic,  diatomic, 
triatomic  alcohols,  &c.,  and  these  are  still  further  subdivided 
according  to  the  class  of  hydrocarbons  from  which  they  are  de- 
rived.    Moreover,  each  alcohol  is  one  of  a  group  of  compounds 
which  may  be  derived  from  each  other  by  simple  reactions,  not 
affecting  the  arrangement  of  the  atoms  in  the  carbon  skeleton 
that  may  be  regarded  as  the  nucleus  of  the  group.     The  com- 
pounds thus  related  have  frequently  little  in  common,  and  in 
more  extended  works  would  be  classed  under  their  appropriate 
heads.     Our  only  object  is  to  exhibit  a  few  of  the  general  prin- 
ciples and  wonderful  relations  which  the  study  of  organic  chem- 
istry has  revealed,  and  this  will  best  be  gained  by  associating 
with  each  class  of  alcohols  those  of  their  derivatives  which  have 
the  same  atomicity. 

MONATOMIC  COMPOUNDS. 
1.  MARSH  GAS  SERIES. 

438.  Alcohols.  —  This  very  important  class  of  compounds 
may  be  regarded  as  derived  from  the  normal  hydrocarbons  of 
the  marsh  gas  series  by  replacing  a  single  atom  of  hydrogen 
with  Ho,  and  consequently  they  are  hydrates  of  the  radicals  of 
the  methyl  series   (40).     Of  these   bodies  the  following  are 
known :  — 

Boiling-point. 

Methylic  Alcohol  CH*0-H  66°.5 

Ethylic  Alcohol  Czff5-0-ff  78°.4 

Propylic  Alcohol  Csff7-0-H  96° 

Butylic  Alcohol  C4ff9-0-ff  109° 


486  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§438. 

Melting-point.        Boiling-point. 

Amylic  Alcohol  C6HU~0-H        —20°  132° 

Hexylic  Alcohol  CGff13-  0-h. 

Heptylic  Alcohol  C7H16-0-ff 

Octylic  Alcohol  C&HlfO-H  178° 

Cetylic  Alcohol  C^H^O-H  50° 

Cerotic  Alcohol  C^H^O-H  79° 

Melissic  Alcohol  C^H^O-H  85° 

The  lower  members  of  the  series  are  liquids,  the  higher  solids, 
and  the  boiling-point  increases  about  19°  for  every  addition  of 
CH^  The  following  reactions  illustrate  the  production  of 
methylic  alcohol  from  marsh  gas  :  — 


4  +  Ol-Ol  =  HGl  +  CfffCl,  [431] 

fCl  +  Ag-0-C2ff30  =  AgCl  +  Cff3-0-C2ff30,  [432] 

-H;  [433] 


and  the  same  method  applied  to  the  homologues  of  marsh  gas 
yields  other  members  of  the  alcohol  series. 

We  may  also  start  with  olefiant  gas,  and  having  combined 
this  with  HGl  we  may  convert  the  C%H5Ql  thus  formed  into 
common  alcohol  by  the  same  series  of  reactions  as  before,  or  we 
may  reach  the  same  result  by  combining  olefiant  gas  with  sul- 
phuric acid  and  distilling  the  product  with  water. 


4  =  H,  C2H5=  02=S02.         [434] 
ff,C2ff5=02=S02  +  H-0-H=  H2=02=S02  +  O2ff5-0-ff.  [435] 

Propylic  alcohol  may  be  obtained  from  O3ff6  by  similar  re- 
actions, but  these  processes  applied  to  the  other  members  of  the 
olefiant  series  either  give  no  results  or  yield  compounds  which, 
although  resembling  the  true  alcohols,  and  isomeric  with  them, 
manifest  in  their  reactions  an  essential  difference  of  molecular 
structure.  These  bodies  have  been  called  pseudo-alcohols. 

By  means  of  the  following  reactions  we  may  ascend  from  one 
member  of  the  alcohol  series  to  the  next  higher  :  — 

fSOt  +  ff20.  [436] 


§439.]    MONATOMIC  COMPOUNDS.  —  MARSH  GAS  SERIES.    487 

K,  C.2Hf  02=S02  +  K-CN=  Kf  02=S02  +  C2&5-  GN.  [437] 

.  [438] 


2C3fffO-ff+  H20  +  2N-2T.  [439] 

Common  alcohol  is  always  obtained  in  the  arts  by  the  fer- 
mentation of  grape  sugar  (480),  and  other  compounds  of  the 
series  are  not  unfrequently  formed  in  small  amounts  during  the 
same  process. 

The  typical  hydrogen  of  the  alcohols  may  be  replaced  by 
sodium  or  potassium. 

2H-  0-  C2H6  +  K-K  =  2K-  0-  C2ff5  +  H-H.     [440] 

An  alcohol  in  which  the  oxygen  has  been  replaced  by  sul- 
phur may  be  obtained  by  the  following  reaction  :  — 


+  K-S-H=  Kf  OfS02  +  C2H&-S-H.  [441] 

This  sulphur  alcohol  is  called  mercaptan,  and  a  corresponding 
selenium  alcohol  is  also  known. 

By  the  action  of  oxidizing  agents  the  alcohols  are  converted 
first  into  aldehydes  and  then  into  acids, 


C2ff5-ffo  +  0  = 

Alcohol.  Aldehyde. 

[442] 
C2ff30-ff+  0  =  C,ffsO-Ho; 

Aldehyde.  Acetic  Acid. 

but  only  in  a  few  cases  can  the  process  be  arrested  at  the  first 
stage. 

439.  Fat  Acids.  —  The  acids  formed  by  the  oxidation  of  the 
monatomic  alcohols  belong  to  a  remarkable  series  of  organic 
compounds,  of  which  more  members  are  now  known  than  of 
any  other.  These  acids  may  be  regarded  as  hydrates  of  the 
oxygenated  radicals  of  the  methyl  series  (40),  (436),  or  as 
formed  from  the  hydrocarbons  homologous  with  marsh  gas  by 
replacing  one  atom  of  hydrogen  with  oxatyl  (416).  The  fol- 
lowing are  known  :  — 


488 


ALCOHOLS  AND   THEIR   DERIVATIVES. 


[§439. 


Melting- 

Boiling- 

poiut. 

point. 

Formic  Acid 

H-O-CHO      or 

Ho-(CO-Hy 

+1° 

100° 

Acetic  Acid 

H-0-C2H30     « 

Ho-(CO-CH8-) 

-J-170 

117° 

Propionic  Acid 

H-0-C3H,0     " 

Ho^CO-C^H,) 

141° 

Butyric  Acid 

H-0-Cfl.O     " 

Ho-(CO-C3H7) 

—20° 

161° 

Valeric  Acid 

H-0-C&H90     " 

Ho-(CO-CtH9~) 

175° 

Caproic  Acid 

H-0-C,HU0   " 

Ho-(CO-C^Hn) 

+5° 

198° 

(Enanthylic  Acid 

H-0-C\H130    " 

Ho-(CO-C6Hl3) 

212° 

Caprylic  Acid 

H-0-CBHraO    « 

Ho-(CO-C,Hl&) 

14° 

236° 

Pelargonic  Acid 

H-O-C^O    « 

Ho-(CO-CzH^) 

18° 

260° 

Capric  Acid 

H-0-C10H190  « 

Ho-(CO-C9Hl9) 

27° 

Laurie  Acid 

H-0-C^H^O  " 

Ho-(CO-CuH23) 

44° 

Myristic  Acid 

H-0-CuHaO  « 

Ho-(CO-CuHa) 

54° 

Palmitic  Acid 

H-0-C16H310  " 

Ho-(CO-C^fI3l) 

62° 

Margaric  Acid 

H-0-C^H^O  « 

Ho-(CO-CuHu) 

60° 

Stearic  Acid 

H-0-Cl6H^p  " 

Ho-(CO-C^H35) 

69° 

Arachidic  Acid 

H-O-C^O  " 

IIo-(CO-CM 

•75° 

Behenic  Acid 

H-0-C^H^O  « 

Ho-(CO-C2lHi3) 

76° 

Cerotic  Acid 

H-O-Cffff^O  " 

Ho^CO-C^H^) 

78° 

Melissic  Acid 

H-0-C^H^O  " 

Ho-(CO-C^H5g) 

88° 

Formic  acid  is  found  in  nettles,  and  is  secreted  by  ants.  Va- 
leric acid  is  found  in  the  valerian  root,  pelargonic  acid  in  the 
essential  oil  of  the  Pelargonium  roseum,  and  cerotic  acid  in 
beeswax.  Chinese  wax  is  cerylic  cerotate,  spermaceti  cetylic 
palmitate,  and  the  natural  fats  are  mixtures  of  salts  of  various 
acids  of  the  group,  in  which  glyceryl,  C3H5,  is  the  basic  radical. 
Several  of  these  acids  may  be  procured  by  the  oxidation  of  al- 
buminous compounds.  Propionic  and  butyric  acids  are  pro- 
duced in  some  kinds  of  fermentation,  and  acetic  acid  is  made  in 
the  arts  in  large  quantities  from  the  products  of  the  dry  distil- 
lation of  wood  and  other  similar  substances. 

The  formation  of  the  fat  acids  by  the  oxidation  of  the  corre- 
sponding alcohol  is  illustrated  by  the  reactions  already  given 
[442].  They  may  also  be  formed  from  the  cyanides  of  the 
alcohol  radicals,  and  the  method  is  interesting  as  indicating 
their  molecular  constitution. 

1  The  student  will  not  fail  to  notice  that  all  dashes  used  in  connection  with 
the  hydrocarbon  radicals  must  refer  exclusively  to  the  carbon  atoms,  since  the 
hydrogen  atoms,  being  united  to  the  carbon  skeleton  by  their  only  bond,  can 
present  no  open  affinity. 


§439.]   MONATOMIC  COMPOUNDS.  —  MARSH  GAS  SERIES.    489 

H-CN  +  HOI  +  2H,0  =  NH,  Ol  +  (H-  CO)  -Ho. 

[443] 
02H6-  CN+  HGl  +  2H20  =  NH4-  Gl  +  (  O2H5-  GO)  -Ho. 

So  also 
C2H6-ON+  K-Ho  +  H20  =  (C2H5-OO)-Ko  +  NH3.  [444] 

On  the  other  hand,  when  the  aramonic  salts  of  these  acids  are 
heated  with  P205  they  are  converted  back  into  the  cyanides  of 
the  radicals  of  the  methyl  series, 

(  OH,-  GO}-(NH,)o  +  2P2  05  =  OH3-  ON+  ±H-  0-PO*  [445] 

and  from  the  cyanide  thus  obtained  the  corresponding  alcohol 
may  be  produced  by  [438],  and  in  this  way  [442]  is  reversed. 
The  acid  may  also  be  converted  into  the  alcohol  by  another 
remarkable  series  of  reactions,  of  which  the  following  series  is 
an  example :  — 

(OHs-00)-Ko  +   (H-GO)-Ko  = 

Potassic  Acetate.  Potassic  Formate. 

(CH3-OO)-H  +  Koz-G0.     [446] 

Acetic  Aldehyde.  Potassic  Carbonate. 

(CH8-00)-H+  H-H  =  02H5-0-ff.  [447] 

The  potassic  salt  of  the  acid  is  first  distilled  with  potassic  for- 
mate, and  the  aldehyde  thus  obtained  transformed  into  alcohol 
by  nascent  hydrogen.  Starting  now  with  ethylic  alcohol,  we 
can  convert  it  into  ethylic  cyanide  by  [436]  and  [437],  and 
then  by  [438]  or  [444]  we  can  produce  propionic  acid.  Thus 
we  are  able  to  pass  from  one  fat  acid  to  the  next  as  from  one 
alcohol  to  the  next,  and  since  formic  acid  can  be  made  directly 
from  its  elements  [374]  the  synthesis  of  this  whole  class  of  or- 
ganic compounds  is,  theoretically  at  least,  possible. 

All  these  reactions  seem  to  indicate  that  the  fat  acids  contain 
the  radicals  of  the  methyl  series  united  to  oxatyl,  and  this  view 
is  rendered  more  probable  by  the  fact  that  sodic  acetate  may  be 
formed  by  the  direct  combination  of  O02  with  sodic  methide. 

(  OHs)-Na  +  002=(  Off,-  CO)  -Nao.          [448] 

Again,  it  appears  that,  when  the  acids  of  this  series  are  acted 
upon  by  nascent  oxygen  in  the  process  of  electrolysis,  O03  is 
21* 


490  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§440. 

formed,  and  the  radical  assumed  to  have  been  previously  united 
to  the  oxatyl  is  thus  set  free. 


2(0ff3-00)-ffo  +  0=  CffB-CHB  +  ff20  +  2G02.  [449] 

If  this  theory  of  the  constitution  of  the  fat  acids  is  correct,  it 
is  obvious  that  if  we  could  replace  the  radical  hydrogen  of  for- 
mic acid  with  the  radicals  methyl,  ethyl,  &c.,  we  should  obtain 
the  successive  members  of  the  series.  The  direct  substitution 
has  not  been  accomplished,  but  with  acetic  ether  an  analogous 
series  of  reactions  has  been  obtained. 

2C,ff5-0-(CO-Cff3)  +  Na-Na  = 

2  C,H5-0-(  GO-CH^Na)  +  H-H.  [450] 

GzH&-0-(GO-CH2Na)  -f  Cff3I  = 

C,H,-0-(GO-G,H5)  +  NaL  [451] 


G2ff5-0-(GO-G3ff7)  +  NaL  [452] 

440.  Formic  Acid,  on  account  of  its  peculiar  constitution  as 
the  first  member  of  the  series,  presents  some  special  reactions 
which  are  highly  instructive.  Thus,  when  heated  with  strong 
sulphuric  acid, 

(H-  GO)  -Ho  =  ff20  +  GO.  [453] 


So  also  when  acted  on  by  chlorine  gas, 

(H-GO)-Ho  +  Gl-Gl  =  2HGI  +  GO?         [454] 
It  even  acts  as  a  reducing  agent, 

(H-GO)  -ffo  +  ffgO  =  ffg  +  ff20  +  G02.     [455] 


441.  Acetic  Acid,  the  acidifying  principle  of  vinegar,  is  the 
best  known  of  all  the  lower  members  of  this  series  of  com- 
pounds, and  the  student  has  already  become  familiar  with  it  in 
many  reactions.  The  remarkable  substitution  products  which 
it  yields  with  chlorine  have  already  been  described  (31),  and 
the  manner  in  which  it  breaks  up  when  acted  on  by  PG15  has 
also  been  illustrated  (29).  By  this  last  reaction  a  chloride  of 
the  assumed  oxygenated  radical  (acetyl)  is  obtained. 


§443.]    MONATOMIC   COMPOUNDS.  — MARSH  GAS  SERIES.  491 

442.  Isomers  of  the  Fat  Acids.  —  It  is  obvious  that  with  the 
higher  members  of  the  acetic  acid  series  one  or  more  isomeric 
modifications  are  possible,  depending  upon  the  different  ways 
in  which  the  atoms  of  the  hydrocarbon  radical  may  be  grouped 
(428).  Such  differences  of  structure  have  been  actually  real- 
ized by  means  of  reactions  similar  to  [450  et  seq.~],  using,  how- 
ever, as  the  starting-point,  the  products  obtained  by  replacing 
two  or  all  three  of  the  hydrogen  atoms  of  the  acid  radical  in 
ethylic  acetate  with  sodium. 

C2ff6-0-(GO-CHNa2)  +  2Cff3I= 

2NaI-\-C2ff5-0-(CO-Off=(Cff3)2).  [456] 


C2ff5-0-(CO-CNa3) 

ZNaI+C2H5-0-(CO-0-(CH3)3).  [457] 

By  acting  on  these  ethylic  salts  with  K-Ho,  the  corresponding 
potassic  salts  are  readily  obtained,  from  which  the  acids  them- 
selves may  be  easily  set  free. 

Now  the  first  of  these  products  is  isomeric,  but  not  identical, 
with  butyric  acid  (boiling  at  152°  instead  of  161°),  and  the 
second  sustains  a  similar  relation  to  valeric  acid.  By  exhibit- 
ing the  symbols  graphically,  the  difference  of  structure  will  be 
made  evident,  and  it  will  appear  that,  although  reactions  like 
[451]  yield  the  normal  acids  of  the  series,  reactions  similar  to 
the  last  must  necessarily  give  the  so-called  iso-acids.  It  can 
also  be  discovered  how  many  isomers  are  possible  in  any  case. 

443.  Ethers.  —  These  compounds  are  the  anhydrous  oxides 
of  the  alcohol  radicals  (40),  and  our  common  ether,  (C^H^^O, 
may  be  taken  as  the  type  of  the  class.  It  is  prepared  by  the 
action  of  sulphuric  acid  on  alcohol,  and  the  process  may  be  di- 
vided into  two  stages :  — 

C2ff5-0-ff+  ff2=02=S02  =  ff,C2H5=02=S02  +  JSg®. 

"458] 
02=S02+C2R5-0-ff=- 


The  alcohol  and  sulphuric  acid,  mixed  in  equivalent  proportions, 
are  heated  in  a  retort,  when  the  water  and  ether  distil  over  to- 
gether, and  if  the  loss  is  supplied  by  fresh  alcohol  (flowing  glowly 
into  the  retort  through  a  tube  adapted  to  the  tqbulature)  the 
same  quantity  of  sulphuric  acid  will  convert  an  unlimited  quan- 
tity of  alcohol  into  ether. 


492  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§444. 

Ether  may  be  reconverted  into  alcohol  by  reversing  the 
above  reaction,  thus  :  — 

(  CJfft)f  0  +  2ff2=  02=S02  =  2ff,  C2ff6=  02=S02  +  IH2(D. 

[459] 
H,  02ff5=  02=S02  +  H-  0-11=  Hf  02=S02  +  @2IH5-CcHll. 

By  using  in  the  second  stage  of  "  etherification  "  an  alcohol 
containing  a  different  radical,  mixed  ethers  as  they  are  termed 
may  in  some  cases  be  obtained. 

H,C5ffn=02=S02+C2ff5-0-ff= 

Hf02=S02  +  C2ff5,C5ffifO.  [460] 

Other  bodies  of  this  class  have  been  formed,  thus  :  — 

2  Cff3-0-ff+  Na-Na  =  2  CH30-Na  +  H-H. 

[461] 
CHz-O-Na  +  C2H5I=  Nal  +  Cff3-0-C2ff5. 

444.  Compound  Ethers.  —  We  include  under  this  head  the 
numberless  salts  of  the  hydrocarbon  radicals  usually  distin- 
guished as  different  kinds  of  ether.  These  bodies  are,  for  the 
most  part,  volatile,  and  have  an  agreeable  odor  which  resembles 
that  of  fresji  fruit,  and  several  of  them  are  used  by  the  confec- 
tioners as  essences.  They  are  produced  by  reactions  similar 
to  those  employed  in  the  preparation  of  metallic  salts. 

C2ff5-Cl  +  Ag-0-O2ff30  =  AgCl  +  C2ff5-0-O2ff30.  [462] 

Argentic  Acetate.  Acetic  Ether. 


.  [463] 

Butyrylic  Chloride.  Butyric  Ether. 

n=  OfS02  +  K-  0-  02H3  0  = 

Potassic  Acetate. 

.  [464] 

Amylic  Acetate. 


H-0~C2ff30  =  C2ff5-0-C2ff30  +  H,0.   [465] 

In  reactions  like  the  last,  when  a  weak  acid  is  unable  by  it- 
self to  produce  the  decomposition  of  the  alcohol,  the  presence 
of  a  strong  mineral  acid  will  sometimes  determine  the  forma- 
tion of  the  ether.  The  reaction  is  then  best  expressed  as  if  in 
two  stages. 


§446.]  MONATOMIC  COMPOUNDS.  —  MARSH  GAS  SERIES.     493 

fOfSOt  =  H,C2ff5=02=S02  +  H,0. 
+  H-0-G7H50  =  [466] 

Benzole  Acid. 

H2=02=S02+C2ff5-0-C7ff50. 

Benzole  Ether. 


HGl  =  G^-Gl  4-  ff20. 

[467] 
0,ff,-Gl  +  H-O-GHO  =  HGl  +  C4H9-0-OffO. 

When  acted  on  by  strong  alkaline  bases  the  compound  ethers 
yield  a  metallic  salt  and  an  alcohol. 

C2ff5-0-C2ff30  +  K-0-ff=K-0-C2H30+C2ff6-0-£r.  [468] 

Since  the  ethers  are  quite  insoluble  in  water,  such  reactions  are 
best  obtained  in  alcoholic  solutions,  and  this  kiud  of  decomposi- 
tion is  frequently  called  saponification.  At  a  high  temperature 
the  ethers  may  be  saponified  by  water  alone. 

445.  Anhydrides.  —  The  simple  and  mixed  ethers  are  anhy- 
drides, but  the  name  is  usually  confined  to  the  oxides  of  the 
acid  radicals.     Acetic  anhydride  may  be^obtained  by  the  fol- 
lowing reaction, 

K-  0-  G2H3  0  +  C2ff3  0-  Gl  =  KOI  +  (  G2ffs  0)2=  0,    [469] 

and  propionic,  butyric,  and  valerianic  anhydrides  may  all  be 
prepared  in  a  similar  way.  Formic  anhydride,  however,  has 
not  as  yet  been  formed.  In  contact  with  water  these  anhy- 
drides dissolve  only  slowly,  in  measure,  as  they  are  converted 
into  the  corresponding  acids. 

446.  Haloid  Ethers.  —  The  term  haloid  means  resembling 
common  salt,  and  is  applied  to  those  compounds  which,  like 
sal^  are  formed  after  the  simple  type  of  HGl,  and  includes  the 
cyanides,  chlorides,  bromides,  &c.,  of  the  hydrocarbon  radicals. 
These  ether-like  bodies  are  formed  in  a  great  variety  of  re- 
actions. 

HGl  =  O2ff&-Cl  +  H20.         [470] 


ll-0-H+  PC13  =  HfOfPOH+  3  O5ffn-OL  [471] 
ff3^PO+5C2ff5-I+  H,0.  {472] 
CH,  +  Gl-  Gl  =  Cff3-  Gl  +  H-  Gl  [473] 


494  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§  447* 

When  acted  on  by  an  alcoholic  solution  of  potash,  all  the 
haloid  ethers,  except  the  cyanides,  are  converted  into  alcohols. 


C5fflf  Cl  +  K-  0-ff=  KCl  +  CJfftfO-H.      [474] 

The  reaction  of  the  cyanides  has  already  been  given  [444]. 

The  haloid  ethers  are  allied  to  the  hydrogen  acids,  and  like 
these  combine  with  ammonia,  and  by  the  action  of  potash  on 
the  salts  thus  formed  various  amines  may  be  obtained. 


NH, 

[475] 


-0-H= 

Ethylamine. 

Ethylic  iodide,  heated  in  a  sealed  tube  with  water,  is  con- 
verted into  common  ether. 


[476] 

Me  thy  lie  chloride,  when  acted  on  by  chlorine,  yields  the  fol- 
lowing substitution  products,  and  it  will  be  noticed  that  the 
boiling-point  increases  in  proportion  as  the  atoms  of  hydrogen 
are  replaced. 

B.  P.  B.  P.  B.  P.  B  p. 

CHj-Cl    —21°,     Cff2Cl2    31°,     CffOls    60°.8,     GC14    78°. 

The  compound  CffOl3  is  called  chloroform,  and  is  an  anaes- 
thetic agent  made  in  large  quantities  by  heating  alcohol  or  wood 
spirit  (methylic  alcohol)  with  a  solution  of  chloride  of  lime 
(282).  When  boiled  with  an  alcoholic  solution  of  potash,  chlo- 
roform is  converted  into  potassic  formiate,  and  chlorine  gas, 
under  the  influence  of  sunlight,  changes  it  into  carbonic  chloride. 

-0-ff=  3KCl+K-0-(CO-ff)+2ff20.  [477] 


Bromoform,  CHBr&  and  lodoform,  OHI&  are  also  known. 

447.  Aldehydes.  —  These  bodies,  already  mentioned  as  the 
products  of  the  imperfect  oxidation  of  the  alcohols  [442],  may 
also  be  obtained  by  distilling  a  mixture  of  potassic  formate  with 
the  potassic  salt  of  the  acid  corresponding  to  the  aldehyde  re- 
quired. 

K-O-(OO-H)  +  K-0-(GO-CH,}  = 

[478] 


Acetic  Aldehyde. 


§  448.]  MONATOMIC   COMPOUNDS.  —  MARSH   GAS   SERIES.      495 

The  aldehydes  are  distinguished  by  a  strong  affinity  for  oxy- 
gen. They  not  only  absorb  oxygen  gas  from  the  air,  but  they 
reduce  argentic  oxide,  and  when  heated  with  alkaline  hydrates 
they  evolve  hydrogen,  passing  in  each  case  into  the  correspond- 
ing acid. 


0  —  H-O-(CO-CHi).        [479]- 

Aldehyde.  Acetic  Acid. 

ff-(00-0ffs)  +  Acr.20  =  ff-0-(CO-Off3)  +  Ag-Ag.  [480] 
ff-(OO-Cff3)  +  K-0-ff=  K-0-(GO-CH3)  +  H-H.  [481] 

By  nascent  hydrogen  (water  and  sodium  amalgam)  the  alde- 
hydes are  converted  back  into  alcohol. 

H-(  G0-0ff3)  +  ff-ff—  O2fls-0-ff.  [482] 

Most  of  them  yield  crystalline  compounds  with  ammonia. 

H-(  GO-Off,)  +  Nff3  =  NHf(  00-0ff3).       [483] 

So  also  by  dissolving  potassium  in  aldehyde  we  obtain  the 
reaction 


2ff-(GO-Off3)  +  K-K=  2K-(OO-Off3)  +  H-H.  [484] 

The  aldehydes  are  named  after  the  corresponding  acids. 
The  first  is  formic  aldehyde  ff-(OO-ff),  and  the  seven  succeed- 
ing terms  of  the  same  series  have  been  obtained.  Of  acetic 
aldehydes  there  are  three  polymeric  modifications.  The  nor- 
mal compound  is  a  very  volatile  liquid,  boiling  at  21°  and  hav- 
ing a  strong  suffocating  odor. 

448.  Ketones.  —  This  name  is  applied  to  a  class  of  com- 
pounds outwardly  resembling  the  alcohols  and  having  a  pleas- 
ant ethereal  odor.  They  are  isomeric  with  the  aldehydes,  but 
differ  from  them  widely  in  their  chemical  relations,  for  they  are 
comparatively  inactive  bodies,  and  show  no  tendency  to  unite 
with  oxygen.  They  are  most  readily  obtained  by  distilling  the 
potassic  or  calcic  salts  of  the  monatomic  acids. 

Oa=0,=(00-0ff3)i=:0a=0f00+(0ffs)f00.  [485] 

Calcic  Acetate.  Acetone. 


Ca*Of(CO-C9ff8)t  =  Ga-OfGO  +  (G2ff5\fGO.   [486] 

Calcic  Propionate.  Propione. 


496  ALCOHOLS  AND  THEIE  DERIVATIVES.  [§449. 

It  will  be  noticed  that  the  two  ketoues  thus  obtained  differ 
by  2  GHz,  although  the  initial  acids  only  differ  by  CH.2  ;  but  by  dis- 
tilling an  intimate  mixture  of  the  two  salts  we  can  obtain  the 
intermediate  term  of  the  series,  namely,  Gff3,02IT5=GO. 

Ketones  can  also  be  obtained  by  acting  on  acetyl  chloride  or 
its  homologues  with  zinc  methide  or  ethide. 

2(Off3-GO)-Cl  +  Zn=(GH3)2=ZnOl2+2(Gff3)2=00.  [487] 

Moreover,  they  have  been  formed  by  the  action  of  carbonic 
oxide  on  sodic  ethide  and  the  homologous  compounds. 

2Na-G2ff5  +  CO  =  Na-Na  -f  (O^fOO.     [488] 

449.  Pseudo-Alcohols.  —  By  the  action  of  nascent  hydrogen 
the  ketones  are  converted  into  compounds  isomeric,  but  not 
identical  with  the  alcohols. 


(  Gff3)2=  00  +  H-H=  (  GH3)f  GH-Ho.         [489] 

The  bodies  of  this  class  are  also  called  secondary  alcohols, 
and  are  distinguished  by  the  prefix  iso.  Their  relations  to  the 
normal  alcohols  are  illustrated  by  the  following  symbols  :  — 

(OH3-Off2)-iro,  (Cff3-GO)-ff,  (GH,-GO}-Ho, 

Ethylic  Alcohol.  Aldehyde.  Acetic  Acid. 


Propylic  Alcohol.  Aldehyde.  Propionic  Acid. 

(  OH3)f  GH-Ho,  (  Gff3)2=  GO. 

Isopropylic  Alcohol.  Acetone. 

As  common  alcohol  passes  by  oxidation  first  into  aldehyde 
and  then  into  acetic  acid  so  normal  propylic  alcohol,  when 
oxidized,  yields  similar  products.  But  under  the  same  con- 
ditions the  isopropylic  alcohol  gives  acetone,  which,  although 
isomeric  with  propionic  aldehyde,  cannot  be  converted  by  fur- 
ther oxidation  into  propionic  acid,  and  it  is  evident  that  such  a 
change  would  not  be  possible  without  a  complete  remodelling 
of  the  molecule.  The  difference  between  these  isomeric  alco- 
hols, indicated  by  their  reactions,  is  still  further  manifested  in 
their  boiling-points,  since  while  the  normal  alcohol  boils  at  96°, 
the  pseudo-alcohol  boils  at  87°.  Besides  the  isopropylic  two 
other  pseudo-alcohols  have  been  obtained  which  probably  be- 
long to  the  same  class. 


§451.]      MONATOMIC  COMPOUNDS.  —  VINYL  SERIES.  497 

Isoamylic  Alcohol  (  CH3,  O3fff  CH)-Ho, 

Isohexylic  Alcohol  (  CH^  CtHf  CH)-Ho. 

Lastly  a  pseudo-alcohol  has  been  discovered,  isomeric  with 
butylic  alcohol,  which  appears  to  be  constituted  after  still  a 
third  type,  and  to  be  the  first  of  a  class  of  tertiary  alcohols. 

Pseudo-butylic  Alcohol  (  C7/3)3=  C-Ho. 

If  we  represent  by  H  any  univalent  hydrocarbon-radical,  the 
general  symbols  of  the  three  classes  of  alcohols  we  have  dis- 
tinguished would  be  as  follows  :  — 


HfC-ffo. 

Primary  Alcohol.  Secondary  Alcohol.  Tertiary  Alcohol. 


2.   VINYL  SERIES. 

450.  Vinylic  Alcohol  —  Acetylene  like  ethylene  dissolves  in 
sulphuric  acid,  and  when  the  product  is  distilled  with  water  we 
obtain  the  hydrate  of  the  radical  vinyl  or  vinylic  alcohol. 


Jf2=02=S02  +  C2ff2  = 

[490] 
ff,C2ff3=02=S02±ff-0-ff=ff2=02=S02 


This  alcohol  is  isomeric  both  with  acetic  aldehyde  and  the 
oxide  of  ethylene. 


>  C2ff4=0. 

Vinylic  Alcohol.  Acetic  Aldehyde.  Ethylenic  Oxide. 

No  acid  has  been  obtained  from  it  by  the  action  of  oxidizing 
agents. 

451.  Allylic  Alcohol.  —  The  second  term  of  the  vinyl  series 
may  be  formed  from  glycerine  by  the  following  reactions. 


-I.  [491] 

Allylic  Iodide. 

AfffOfC,0,  =  2A9I+  (08ffs)fOfOaOf  [492] 

Argentic  Oxalatc.  Allylic  Oxalate. 

0,  +  2  ffsN= 

,ff5-0-ff.  [493], 

Oxamide.  Allylic  AlcohoL 

RF 


498  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§452. 

When  dehydrated  by  phosphoric  anhydride  (184)  this  alcohol 
gives  allylene  the  second  member  of  the  acetylene  series. 

(C&)-0-ff—  H20  =  Csff4.  [494] 

Oil  of  garlic  is  the  sulphide  of  allyl  (  C3ff5)2=S  and  oil  of 
mustard  the  sulphocyanate  C&H6~S-CN. 

When  acted  on  by  oxidizing  agents,  allylic  alcohol  yields 
both  an  aldehyde  and  an  acid,  and  the  following  symbols  indi- 
cate the  relations  and  probable  constitution  of  the  three  bodies. 


o,     (Cff2=CH-CO)-H, 

Allylic  Alcohol.  Acrolein  (Aldehyde).  Acrylic  Acid. 

452.  Acrolein  is  formed  abundantly  during  the  dry  distil- 
lation of  fats  or  similar  glycerides  (474),  and  the  pungent  odor 
of  its  vapor,  so  intensely  irritating  to  the  eyes,  is  familiar  to 
every  one.  It  may  be  best  procured  by  the  action  of  dehy- 
drating agents,  such  as  phosphoric  anhydride  or  sulphuric  acid, 
on  glycerine,  from  which  it  differs  by  2H2  0. 


ot  —  2ff20  =  (CSfCff-CO)-ff.  [495] 

Glycerine.  Acrolein. 

453.  Acrylic  or  Oleic  Series  of  Acids.  —  Acrylic  acid  is  the 
first  member  of  a  large  and  important  series  of  acids,  which 
are  associated  with  the  acids  of  the  acetic  series  in  the  natural 
fats  and  oils.  Only  those  members  of  the  series  are  included 
in  the  following  list  which  we  have  reason  to  believe  are  con- 
stituted like  acrylic  acid.  Of  the  constitution  of  the  other  fat 
acids  of  this  class  we  have  as  yet  no  knowledge. 

Acrylic  Acid  C3ff402  or  Ho-(CO  CH-C  JT2), 

CrotonicAcid  C4ff602  "  Ho-(00-CH=C2H^ 

Angelic  Acid  C5ff802  «  ffo-(CO-Cff*CJ%), 

Pyroterbic  Acid  <76#10  02  «  Ho-(  CO-  CH-  C4ff8), 

Oleic  Acid  <718#34  02       «         m-(CO-Cff*Cuffn). 

These  acids  are  closely  allied  to  those  of  the  acetic  series. 
Acrylic  acid  under  the  influence  of  nascent  hydrogen  changes 
into  propionic  acid,  and  when  acted  on  by  bromine  it  yields  a 
simple  derivative  of  the  same  compound. 


§454.]      MONATOMIG  COMPOUNDS.  —  VINYL  SERIES.  499 

Ho-(GO-GH-GH,} 


[496] 
=  ffo-(CO-C2ffsBr2). 

Moreover,  when  heated  with  caustic  potash  all  the  acids  of 
the  above  list  break  up  into  two  acids  of  the  acetic  series,  one 
of  which  is  always  acetic  acid  itself. 

Ho-(GO-GH-GH2)  +  2K-0-ff= 

+  Ko-(GO-H)  +  H-H.  [497] 


Ho-(GO-GH-G2H,)  +  2K-0-ff= 

Ko-(GO-GHB)  +  Ko-(CO-Off3)  +  H-H.  [498] 

2K-0-H  = 
-GHz)  +  Ko-(CO-02ff5)  +  H-H.  [499] 

2K-0-ff= 

-f  Ko-(CO-O3ff7)  +  H-H.  [500] 


Ko-(GO-C^H^  +  H-H.  [501] 

Salt  of  Palmitic  Acid. 

The  alkali  appears  to  act  on  the  defines  (430),  assumed  to 
exist  in  the  radicals  of  these  compounds,  and  replaces  them 
with  HK  thus  forming  acetic  acid  in  every  case,  while  at  the 
same  time  it  converts  the  olefine  itself  into  another  acid  of  the 
acetic  series. 

454.  Secondary  Acids.  —  Acids  isomeric  with  those  of  the 
acrylic  series  have  been  obtained  by  means  of  reactions  which 
indicate  the  structure  of  the  resulting  molecules,  and  a  com- 
parison of  the  reactions  of  these  artificial  products  with  those 
of  the  normal  acids  shows  that  the  rational  symbols  we  have 
assigned  to  the  latter  must  be  essentially  correct.  The  sym- 
bol of  oxalic  ether  may  be  written  Et-0-(GO-GO)-0-Et, 
and  there  are  good  reasons  for  writing  the  symbols  of  the 
zinc  compounds  of  the  monad  radicals  (324)  thus,  (^wH)'Hi 
indicating,  as  is  undoubtedly  the  case,  that  the  group  (Znft)- 
acts  as  a  monad  radical.  When  now  a  body  of  this  class  acts 
on  oxalic  ether,  the  following  reaction  takes  place  :  — 

Et-0-(GO-GO)-0-Et  +  2(^nH)-E  = 

Et-0-(GO-G^)-0-(ZnW)  -{-  Et-O-(ZnW).  [502] 


500  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§455. 

If  next  water  is  added,  the  product  of   the  last  reaction 
undergoes  a  still  further  change, 


-H,  [503] 

and  the  whole  effect,  as  will  be  seen,  is  to  replace  one  atom  of 
oxygen  in  the  radical  of  oxalic  acid  with  two  atoms  of  a  radical 
of  the  methyl  series.  Lastly,  if  we  subject  one  of  these  acids, 
thus  synthetically  obtained,  to  a  dehydrating  agent  (PO13  or 
P205),  the  result  is  an  isomer  of  the  acrylic  series. 

Et-0-(CO-C^-0-H—  H20  =  &-0-(CO-Cfcto).  [504] 

Here  £R  stands  for  a  dyad  radical  of  the  olefiant  series,  and 
the  symbols  of  the  compounds  which  have  been  obtained  in 
this  way  are  given  below.  By  comparing  these  with  the 
symbols  of  the  normal  isomers,  the  difference  of  structure  will 
be  evident. 

Secondary  Acids.  Normal  Acids. 

Methyl-acrylic  Acid  H-0-(CO-C(CH^CHZ)  H-0-(CO-CH=C2HJ 
Methyl-crotonic  "  H-0-(CO-C(CH^CtH^  H-0-(CO-CH=CJQ 
Ethyl-crotonic  "  JJ-0-(  CO-  C(  <?,#,)=(?,  ffj  H-0-(CO-CH--C\H^ 

When  treated  with  potash,  the  secondary  acids  break  up  like 
the  normal  compounds,  but  they  only  give  acetic  acid  when  the 
dyad  radical  is  ethylene,  and  after  writing  these  reactions,  ac- 
cording to  the  models  given  above,  it  will  be  seen  not  only  that 
these  facts  confirm  the  opinion  already  expressed  in  regard  to 
the  nature  of  the  change,  but  also  that  the  close  coincidence  be- 
tween theory  and  observation  gives  strong  grounds  for  believing 
that  we  have  gained  positive  knowledge  in  regard  to  the 
structure  of  the  bodies  we  have  been  studying. 

455.  Tertiary  Acids.  —  By  means  of  the  following  reaction 
a  second  isomer  of  crotonic  acid  has  been  obtained,  which  must 
have  a  structure  differing  from  either  of  the  other  two  condi- 
tions of  this  compound.  Compare  [444]. 


K-0-H-\-  H20  = 
(Cff2=CH-Cff<fCO)-0-K+Arff3.  [505] 

Potassic  ft  Crotonate. 


§457.]    MONATOMIC  COMPOUNDS.  —  PHENYL  SERIES.          501 


3.   PHENYL  SERIES. 

456.  Benzole  Alcohol  —  If  the  peculiar  grouping  of  the 
carbon  atoms  represented  in  Fig.  c  (428)  is  an  essential  char- 
acter in  the  structure  of  the  radical  phenyl  and  its  homologues, 
it  is  obvious  that  the  lowest  normal  alcohol  of  this  series,  formed 
after  the  type  of  common  alcohol,  must  have  the  composition. 
represented  by  the  symbol  (C6ff5-Cff2)-0-ff.  This  body  is 
Benzoic  Alcohol,  and  the  corresponding  aldehyde  and  acid  are 
the  well-known  compounds  Oil  of  Bitter  Almonds  and  Benzoic 
Acid. 


,          (C6ff5-CO)-0-ff. 

Benzoic  AicoaoL  Oil  of  Bitter  Alnaonds.  Benzoic  Acid. 

Benzoic  alcohol  may  be  prepared  by  treating  oil  of  bitter 
almonds  with  an  alcoholic  solution  of  potassic  hydrate. 


(CQff5-Cff2)-0-ff. 

It  may  also  be  made  from  toluol  (methyl-phenylic  hydride) 
(434).  " 

CaHf  Off,  +  Ol-  Cl  =  (  Oefff  Off,)-  01  +  HOI. 

Toluol.  Toluic  Chloride. 

(  C6ff5-  Cff2)-  Cl  +  K-  0-ff=  KCl  +  (  CQH5-  Off,)-  Off. 

Moreover,  benzoic  acid,  when  acted  on  by  nascent  hydrogen, 
is  reduced  in  part,  first  to  benzoic  aldehyde  (oil  of  bitter  al- 
monds), and  then  to  benzoic  alcohol. 

The  essential  oil  of  cumin  is  a  mixture  of  cymol,  Cwffu^  and 
cuminic  aldehyde,  from  which  may  be  derived  on  the  one  side 
cumylic  alcohol  homologous  with  benzoic  alcohol  and  on  the 
other  cuminic  acid  homologous  with  benzoic  acid. 


(  Cgffn-  CffJ  -0-H,         (  O^Hn-  CO}  -H,         (  C»ffn-  C0)-0-ff. 

Cumylic  Alcohol.  Cuminic  Aldehyde.  Cuminic  Acid. 


Sycocerylic  alcohol  (C^H^-Cff^-O-ff^  obtained  from  a  resin 
brought  from  New  South  Wales,  is  supposed  to  be  another 
member  of  this  series. 

457.  Phenols.  —  By  comparing  the  symbols  of  the  normal 
alcohols,  of  either  class,  as  given  above,  or  still  better  when 


502  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§457. 

exhibited  by  one  of  the  graphic  methods,  the  student  will  see 
that  the  peculiarity  in  their  structure  consists  mainly  in  the  cir- 
cumstance that  two  atoms  of  hydrogen  are  attached  to  the 
same  carbon  atom,  to  which  the  atom  of  hydroxyl  is  also  united, 
so  that  when  these  atoms  of  hydrogen  are  replaced  by  an  atom 
of  oxygen,  the  radical  oxatyl  H-Q-OO  is  formed  in  the  mole- 
cule, and  this,  as  has  been  shown,  appears  to  be  the  acidifying 
principle  of  all  the  organic  acids.  Hence  by  a  very  simple  re- 
placement, which  does  not  alter  the  molecular  structure,  the 
alcohol  changes  into  an  acid. 

Such  now  is  the  structure  of  benzoic  alcohol,  but  such  would 
not  be  the  condition  if  the  Ho  were  united  directly  to  one  of 
the  carbon  atoms,  which  form  the  nucleus  of  the  radical 
phenyl,  and  it  can  easily  be  seen  that  the  resulting  product, 
C6HsO-H)  could  not  change  into  an  acid,  at  least  of  the  oxatyl 
type,  without  disturbing  the  peculiar  atomic  grouping  shown  in 
Fig.  c  (428).  Compounds  thus  constituted  are  called  Phenols. 

The  compound  C^H^O-His  a  well-known  commercial  pro- 
duct, called  carbolic  acid.  The  more  appropriate  name  is 
phenylic  alcohol,  since  it  is  a  secondary  or  pseudo-alcohol  of  the 
phenyl  series,  differing  from  the  true  alcohols  in  that  it  does  not 
yield  by  oxidation  a  homologue  of  benzoic  acid.  As  we  might 
expect,  however,  the  different  hydrogen  atoms  of  the  radical 
may  be  replaced  by  Cl,  Br,  or  NO&  and  a  great  number  of 
substitution  products  may  be  thus  obtained,  of  which  the  best 
known  is  the  so-called  Picric  Acid  (C6ff2(N02)3)-O-If. 

Phenylic  alcohol  is  one  of  the  products  of  the  dry  distillation 
of  coal,  and  it  is  procured  for  the  arts,  from  the  coal-tar  of  the 
gas-works.  It  may  also  be  formed  by  distilling  salicylic  acid 
with  baryta  or  lime,  or  by  the  action  of  nitrous  acid  on  aniline 
(167).  ' 


H-0-(  Cg-C<sH4)-O-H+  OaO  = 

Salicylic  Acid.  Phenylic  Alcohol. 

[506] 
H*CJI?N+  H-O-NO  =  C6ff5-0-ff+  ff20  +  N-N. 

Aniline.  Nitrous  Acid. 

Phenylic  alcohol  smells  like  wood-tar  creosote,  and  is  an 
equally  powerful  antiseptic  agent.  Indeed,  it  constitutes  the 
greater  part  of  the  so-called  coal-tar  creosote.  There  is  some- 
times associated  with  it  a  small  quantity  of  an  homologous  com- 


§458.]    MONATOMIC  COMPOUNDS.  —  PHENYL  SERIES.          503 

pound,  which  has  been  named  cresylic  alcohol,  and  this  is  the 
only  other  phenol  which  has  as  yet  been  obtained.  It  closely 
resembles  the  first,  has  the  symbol  C7H7-0-H,  and  is  therefore 
isomeric  with  benzoic  alcohol.  The  student  should  seek  to 
exhibit  by  graphic  symbols  the  difference  in  the  structure  of 
these  two  isomeric  compounds,  on  which  the  wide  differences  in 
their  properties  and  chemical  relations  depend,  and  thus  show 
also  why  a  normal  alcohol  isomeric  with  phenylic  alcohol  can- 
not be  produced. 

458.  Acids  of  the  Phenyl  Series.  —  Benzoic  acid,  formerly 
exclusively  obtained  by  sublimation  from  gum  benzoin,  is  now 
more  frequently  procured  from  hippuric  acid  (168),  which  is 
found  abundantly  in  the  urine  of  herbivorous  animals.  When 
hippuric  acid  is  boiled  with  hydrochloric  acid,  the  radical  ben- 
zoyl  (C7H50)  in  this  amide  changes  place  with  HofJf-O-ff, 
and  the  products  are  glycocol  and  benzoic  acid.  Only  two 
other  acids  of  this  series  are  known.  The  normal  series  proba- 
bly includes 

Benzoic  Acid      H-0-(CO-C6ff5), 

ToluylicAcid      H-0-(CO-C7H7)    or  H-0-(CO-CA-GH,), 

CuminicAcid      H-0-(CO-O9ffu)  or  H-0-(CO'C6H4CZH7). 

This  class  of  compounds  has  been  comparatively  little  studied, 
and  future  investigation  will  probably  bring  to  light  not  only 
other  members  of  the  series,  but  also  other  series  of  related 
acids,  differing  from  the  normal  compounds  by  peculiarities  of 
structure  or  slight  variations  in  composition.  One  such  com- 
pound is  already  known,  and  this  bears  the  same  relation  to 
benzoic  acid  that  crotonic  acid  bears  to  acetic  acid, 


ff-0-(CO-Cff3),  H- 

Acetic  Acid.  Crotonic  Acid. 


H-  0-(  CO-CJQ,  H-  0-(  CO-  G,Hf  O2ff4)  ; 

Benzoic  Acid.  Cinnamic  Acid. 

and  when  heated  with  potassic  hydrate  cinnamic  acid  breaks  up 
into  benzoic  and  acetic  acids,  thus  :  — 


K-0-(CO-CH3)  +  H-H.  [507] 


504  ALCOHOLS  AND   THEIK  DERIVATIVES.  [§459. 

Salicylic  acid  is  another  compound  belonging  to  the  phenyl 
group,  and  its  relation  to  benzoic  acid  is  indicated  below.  The 
volatile  oil  of  meadow-sweet  (Spircea  ulmaria)  is  supposed  to 
be  the  aldehyde  of  this  acid,  and  the  oil  of  wintergreen,  called 
also  chequer-berry  (Gaultheria  procumbens),  is  methyl  salicylic 
acid. 

H-  0-(  CO-  C6ff5),  H-  0-(  CO-  O«ff4)-  0-H, 

Benzoic  Acid.  Salicylic  Acid. 


H-(CO-C«H4}-0-H,  H-( 

Oil  of  Meadow-sweet  Oil  of  Wintergreen. 

These  compounds,  however,  being  diatomic,  more  properly 
belong  under  the  next  head. 

DIATOMIC  COMPOUNDS. 

459.  Glycols.  —  The  dyad  radicals  of  the  ethylene  series 
may  combine  with  two  atoms  of  hydroxyl,  and  the  diatomic 
hydrates  thus  formed'constitute  an  interesting  class  of  alcohols 
which  are  usually  called  glycols,  and  whose  relations  to  the 
water-type  have  been  already  explained  (41).  The  following 
reactions  illustrate  three  of  the  methods  by  which  these  bodies 
may  be  produced  :  — 

1.  O2ff4  +  Br-Br  =  O2ff4=Br2.  [508] 

2AgBr+  O2ff4=02=(C2ff30)2.  [509] 
3.    C2Hf Of(  C2ff3 0)2  +  ZK-0-H= 

Diacetic  Glycol.  2K-0-(O2HS0)  +    C^Offf^    [510] 

Ethyl  Glycol. 

Monochlorhydrine  of  Glycol. 

2.  CJSfHo,  Cl  -f  Ay- 0-  02ff3  0  = 

AffOl+  C2ff4=02=(C2H30),ff.  [512] 

3.  C2Hf Of(  O2ff3 0),ff+  K- 0-ff= 


K-0-C2ff30+  C2ff4=02=ff2.  [513] 

Ethyl  Glycol. 


-f  H-H=  HOI  -4-  C,H^Offf2.  [514] 

Monochlorhydrine  of  Glycerine.  Propyl  Glycol        L  J 

The  normal  glycols,  like  all  normal  alcohols,  are  easily  oxi- 


460.]  DIATOMIC  COMPOUNDS.  505 

dized,  and  on  account  of  their  diatomic  nature  a  reaction  simi- 
lar to  [442]  may  be  once  repeated  with  each  of  these  bodies. 
Every  such  glycol  thus  yields  two  acids,  whose  relations  may 
be  best  indicated  by  writing  the  symbols  as  below  :  — 


Eihylic  Glycol. 

H-0-(GO-CH,}-0-H, 

Glycollic  Acid. 

H-0-(CO-COyO-H, 

Oxalic  Acid. 

HfCHfrO-H, 

Propylic  Glycol. 


Paralactic  Acid. 

H-0-(CO-CHfCO)-0-H, 

Malonic  Acid.      ' 

2yO-H, 

Butylic  Glycol. 

--(-Z 

H-0-(CO-C2ff4-CO)-0-ff. 

Succinic  Acid. 

In  these  symbols  those  hydrogen  atoms  which  are  associated 
with  CO  are  strongly  basic,  and  those  which  are  associated 
with  CH2,  although  also  typical  and  replaceable  under  certain 
conditions,  cannot  be  displaced  by  the  usual  metathetical  meth- 
ods (21).  In  this  we  find  the  explanation  of  the  fact  stated 
in  (41),  that  the  acids  homologous  with  glycollic  acid  are  only 
monobasic,  although  diatomic  and  the  acids  homologous  with 
oxalic  acid,  both  dibasic  and  diatomic.  Of  the  glycols  included 
in  the  list  given  in  the  section  just  referred  to  only  the  first  is 
supposed  to  have  the  constitution  exhibited  above.  It  is  prob- 
able that  in  the  others  the  atoms  are  differently  arranged. 

The  following.derivatives  of  ethylic  glycol  will  further  illus- 
trate the  chemical  relations  of  this  class  of  compounds  :  — 

Cyanhydrine  C2ff4=ffo,CN, 

Bromhydrine 

Dibromhydrine  (ethylene  dibromide) 

Bromo-ethylic  Glycol  <72#4=(  C9ffs)  0,Br, 

Sulphur  Glycol  C2ff4=S2=ff2. 

Compare  also  the  products  of  [509],  [511],  and  [512]. 
460.   Ethylenic    Oxide  or  Ether,  which   has   already  been 
mentioned  as  isomeric  with  both  vinylic  alcohol  and  acetic 
22 


506  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§461. 

aldehyde,  is  another  of  the  derivatives  of  ethylic  glycol.  It 
may  be  produced  thus :  — 

+  HGl  —  C2ff4=ITo,Gl  +  ff20. 

[515] 
-0-H=  C2ff4=0  +  ff20  +  KCl. 

Ethylenic  Oxide. 

The  following  reactions  illustrate  the  remarkable  relations 
of  this  compound  :  — 

C2ff4=0  +  H-H  =  C2ff5-0-H.  [51 6] 

C2HfO  +  0=0  =  H-0-(CO-CH2)-0-H.      [517] 

C2Hf  0  +  H-Cl  =  C2fffffo,  Cl.  [5 1 8] 

C2Hf  0  +  R2  0  =  O2ff4=  0./H2.  [51 9] 

It  precipitates  many  oxides  from  solutions  of  their  salts. 

MgCl2  +  2C2ff4=0  +  2Jf20  = 

2C2fffffo,Cl+ Mg=02=ff2.  [520] 

By  expressing  these  reactions  in  a  graphic  form  the  student 
will  see  that  they  are  all  possible  without  a  disruption  of  the 
original  molecule,  and  this  accounts  for  the  great  difference 
between  the  behavior  of  ethylenic  oxide  and  that  of  ethylic 
ether,  which  in  other  respects  is  similarly  constituted. 

461.  Condensed  Glycols.  —  The  peculiar  constitution  of 
ethylenic  oxide,  just  referred  to,  gives  rise  to  a  class  of  glycols 
in  which  the  basic  radical  consists  of  two  or  more  atoms  of 
ethylene  soldered  together  by  atoms  of  oxygen  (38).  Thus, 
representing  ethylene  by  Et  —  C2ff4,  we  have, 

Glycol  Et--OfH2, 

Diethylenic  Glycol    (Et-0-Et)=OfH2, 
Triethylenic  Glycol   (Et-0-Et-O-EtyOfH* 
Tetrethylenic  Glycol  (Et-0-Et-0-Et-0-Et)--OfH» 
Pentethylenic  Glycol  (Et-0-Et-0-Et-0-Et-0-Et]-OfH2, 
Hexethylenic Glycol  (El- 0-Et- O-Et-O-Et-O-Et-O-Et)* 02=ff2. 

These  bodies  are  formed  by  direct  synthesis  when  glycol  and 
ethylenic  oxide  are  heated  together  for  many  days  in  sealed 
tubes,  but  they  are  more  readily  produced  by  the  following 
reactions :  — 

o,Br,         [521] 


§462.]  DIATOMIC  COMPOUNDS.  507 

C2fffffo2=(C2fftO-C2ff4)=ffo2+ff-Br,  [522] 
(  C2ff4-  0-  O2ff4}=Ho2  = 


,  [523] 
and  so  on. 

The  last  reactions  are  also  obtained  by  heating  together  the 
original  factors  in  closed  tubes.  The  several  changes  succeed 
each  other,  and  thus  more  and  more  complex  molecules  are 
gradually  built  up.  However  great  the  condensation,  these 
condensed  molecules  contain  but  two  typical  atoms  of  hydro- 
gen, and  when  oxidized  only  four  of  the  H  atoms  in  the  radi- 
cal can  be  replaced  with  oxygen  as  in  the  normal  glycol.  At 
least  this  is  true  of  diethylenic  and  triethylenic  glycol,  and  with 
these  alone  the  reactions  have  been  studied.  The  symbols  of 
the  acids  resulting  from  the  oxidation  in  the  two  cases  may  be 
written, 

(C2ff40~C202)=02=ff2,      and      (C^fff  0-0^-0^0^  Of  J3^ 

The  compound  (O2ff4-0-O2ff4)  =  02  is  also  known,  and  these 
remarkable  bodies  derive  a  special  interest  from  the  fact  that 
the  study  of  the  phenomena  which  they  present  has  furnished 
the  key  to  the  explanation  of  the  more  complex  phenomena  of 
the  same  kind  with  which  we  are  already  familiar  in  the  min- 
eral kingdom. 

462.  Monobasic  Acids.  1.  Lactic  Family.  —  This  family  of 
acids,  which  represents  the  first  stage  in  the  oxidation  of  the 
glycols,  is  at  the  present  time  especially  interesting,  because  the 
phenomena  of  isomerism  have  been  here  studied  with  more 
success  than  in  any  other  class  of  compounds  of  equal  com- 
plexity. According  to  our  view,  the  normal  glycol  is  one 
which  admits  of  two  degrees  of  oxidation,  as  represented  in 
(459).  Such  a  glycol  may  be  represented  by  the  general 
symbol  Ho-(  Cff2(  Cff2)n-Cff2)-Ho,  where  (  CH2)n  stands  for  any 
olefine,  and  common  glycol  is  the  first  term  of  the  series,  for 
which  n  =  o.  The  glycols  actually  known,  however,  with  the 
exception  of  the  first,  belong  to  a  different  type,  represented  by 
the  symbol  Jfo-(Cff2Cff\&)-ffo,  in  which  U  stands  for  a  radi- 
cal of  the  methyl  series,  and  which  is  capable  of  variation, 
not  only  by  changing  this  radical,  but  also,  as  in  the  normal 
series,  by  the  addition  of  (Cff2)n  between  the  two  carbon  atoms 


508  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§463. 

of  the  original  type.  Moreover,  it  is  evident  that  we  might 
have  still  a  third  class  of  glycols  corresponding  to  the  general 
symbol  Ho-(GH,-(GH2)n-G^2}-Ho. 

From  these  three  classes  of  glycols  we  should  evidently  ob- 
tain, at  the  first  stage  of  oxidation,  three  classes  of  acids,  thus  :  — 

Normal.  Secondary.  Tertiary. 

Ho-(GO-GK2)-Ho, 

Normal  Olefine. 

Ho-(  CO-(  GH2 

Secondary  Olefine. 

Ho-(  GO-(  GH2)n- 

Tertiary  Olefine. 


and  the  term  olefine  may  be  appropriately  used  to  distinguish 
the  succeeding  members  of  each  series  from  the  first.  More- 
over, it  is  equally  evident  that  by  replacing  with  univalent 
radicals  the  hydrogen  of  the  non-basic  hydroxyl  we  may 
obtain  a  whole  group  of  acids  corresponding'  to  each  of  the 
members  of  the  above  scheme.  These  last  acids  we  shall  call 
etheric,  and  we  will  next  endeavor  to  show  that  the  symbols 
which  have  been  assigned  to  the  known  members  of  the  lactic 
family  of  acids  are  legitimately  deduced  from  observed  facts. 

463.  Normal  Acids.  —  Only  three  members  of  this  series 
are  known. 

Glycollic  Acid  Ho-(GO-CH2}-Ho, 

Paralactic  Acid  Ho-(GO-GH2GH2}-Ho, 

Paraleucic  Acid  Jfo-(GO-(GH2)4-CIf2)-iro. 

The  symbol  of  glycollic  acid  may  be  inferred  from  that  of 
glycol,  since  the  acid  is  a  product  of  the  direct  oxidation  of  this 
diatomic  alcohol.  The  symbol  of  paralactic  acid  may  be  re- 
ferred back  to  that  of  ethylene,  which  we  assume  to  be 
(GfffCff2),  by  means  of  the  following  reactions  :  — 

1.  (CfffCffJ  +  COC12  =  Cl-(GO-Off2-Cff2)-Cl. 

2.  Gl-(GO-Gff2-Cff2)-Gl+3Kffo  =  [524] 

/3  Chloropropionylic  Chloride. 

Ko-(GO-GH2Gffs)-Ho  +  2KGI  +  ff20. 

Potassic  Faralactate. 


§464]  DIATOMIC  COMPOUNDS.  509 

So  also 


CN-(  Cff2-Cff2)-ffo  +  KHo 

Cyanhydrine.  ^  CQ-CHfCH^Bo  +  NffB.    [525] 


Fotassic  Paralactate. 

The  body  called  paraleucic  acid  was  formed  by  reactions  simi- 
lar to  [524],  using  amylene  instead  of  ethylene,  but  it  has  not 
yet  been  completely  investigated. 

464.  Secondary  Acids.  —  This  series  includes  the  most  im- 
portant acids  of  the  lactic  family,  and  corresponds  to  the  series 
of  known  glycols.  For  this  reason  its  members  are  regarded 
by  Frankland  as  the  normal  compounds.  The  following  are 
here  classed  :  — 

Gly  collie  Acid  Ho-(CO-CHH)-Ho, 

Lactic  Acid  Ho-(CO-CHMef-Ho. 

Oxybutyric  Acid  Ho-(CO-CHEt}l-Ho, 

Valerolactic  Acid  Ho  -(  CO  -  CffPr)1  -Ho, 

Leucic  Acid  Ho-(CO-CHBu?-Ho. 

Glycollic  acid  may  be  regarded  as  belonging  to  both  the  nor- 
mal and  secondary  series.  Under  certain  conditions  it  is  formed 
in  the  oxidation  of  common  alcohol. 

2ffo-(Cff2Cff2H)  +30=0  = 

Aicohoi.  2ffo-(CO-Cff2)-ffo-\-2ff20.  [526] 

Glycollic  Acid. 

The  constitution  of  lactic  acid  is  made  evident  by  the  follow- 
ing considerations.  It  has  already  been  shown  that  the  symbol 
of  aldehyde  must  be  H-(CO-Cff3).  When  this  is  acted  on  by 
PC15  we  obtain  a  compound  isomeric  with  ethylene  chloride  by 
the  reaction 

H-(CO-CHZ)  +  PG15  =  Clf(Cff-Cff9)  +  POC13.  [527] 

Aldehyde.  Ethylidene  Chloride. 

This  product,  however,  differs  from  ethylene  chloride  both 
in  its  physical  and  chemical  properties,  and  it  must  therefore 
be  the  chloride  of  a  distinct  radical,  to  which  has  been  given 
the  name  of  ethylidene.  Moreover,  the  mode  of  its  production 
(190)  leaves  no  doubt  in  regard  to  its  constitution,  and  then  by 


510  ALCOHOLS  AND   THEIR  DEKIVATIVES.  [§465. 

exclusion  we  fix  the  symbol  of  ethylene  as  well;  for,  as  is 
evident,  the  atoms  O2ff4,  to  form  a  dyad  radical,  must  be 
grouped  in  one  or  two  ways,  either 

•(CHfCH^  or  =(CH-CH&). 

Ethylene.  Ethylidene. 

Now,  as  the  cyanhydrine  of  ethylene  yields  paralactic  acid, 
so  the  cyanhydrine  of  ethylidene  yields  common  lactic  acid. 


Ho,CN=(CH-Me}  +  K-Ho 

Cyanhydrine  of  Ethylidene.  RQ  _(  CO-CHMfyHo  +  NH^.    [528] 

Salt  of  Lactic  Acid. 

We  can  now  interpret  the  following  reaction  by  which  lactic 
acid  is  obtained  from  propionic  acid  :  — 

1.  Ho-(  CO  CHZ-  CH3)  +  Gl-  Cl  = 

Propionic  Acid.  ffo-(CO-CffCl  ~CH3)  +  HCl 

Chloropropionic  Acid.  f  5  2  9  ~1 

2.  Ho-(CO-CHCl-Me)  +  2Kffo  = 

Ko-(CO-CHMe)-Ho  +  KCl  +  H20. 

We  are  thus  able  to  show  to  what  part  of  the  radical  of 
propionic  acid  the  hydrogen  atom  replaced  by  chlorine  be- 
longed. Moreover,  it  is  evident  that  the  acid  which  would  be 
obtained  by  the  action  of  water  on  /3  chloropropionylic  chloride 
(463)  must  differ  from  that  formed  as  above,  and  we  can  under- 
stand the  reason  why.  Lastly,  since  lactic  acid  has  also  been 
formed  by  the  oxidation  of  propylic  glycol,  we  conclude  that 
the  constitution  of  this  body  must  be  Ho-(CH%CHMe)-Ho,  as 
intimated  in  (462). 

For  the  methods  by  which  the  constitution  of  the  other 
members  of  this  series  has  been  established  we  must  refer 
the  student  to  more  extended  works.  The  examples  given 
are  sufficient  to  illustrate  the  general  course  of  the  reasoning. 

465.  Etheric  Secondary  Acids.  —  No  secondary  olefine  acids 
are  known,  but  by  simple  metathetical  methods  we  can  easily 
replace  the  hydrogen  of  the  non-basic  hydroxyl  in  the  com- 
pounds of  this  series  with  various  radicals,  and  the  following 
bodies  will  serve  as  examples  of  the  products  thus  obtained:  — 

Methyl-glycollic  Acid  Ho-(CO-CHJ)-Meo, 

Ethyl-lactic  Acid  Ho  -(  CO  -  CHMe)-Eto, 

Aceto-lactic  Acid  Ho  -(CO-  CHMe)-Aco.1 


§469.]  DIATOMIC  COMPOUNDS.  511 

466.    Tertiary  Acids.  —  The  following  are  known  :  — 
Dimethoxalic  Acid  Ho  - 


Ethomethoxalic  Acid  Ho-(CO-CMeEt}-Ho, 

Diethoxalic  Acid  Ho  -(CO-  GEt^-Ho. 

Our  knowledge  of  the  constitution  of  these  acids  is  based  on 
the  beautiful  synthetical  method  (454)  by  which  they  were 
produced  by  Professor  Frankland,  who  has  also  obtained 
etheric  acids  belonging  to  this  division,  but  no  corresponding 
olefines  have  been  discovered. 

467.  Isomerism  in  the  Lactic  Family.  —  The  number  of  pos- 
sible isomeric  combinations  in  this  family  of  acids  is  evidently 
infinite.  The  following  are  two  of  the  known  examples  :  — 


Ho-(CO-CH,-CH2)-Ho, 


Paralactic  Acid. 


Ho-(CO-CHMe)-Ho, 


Lactic  Acid. 


Ho-(CO-GH^-Meo, 

Methyl-glycollic  Acid. 


Ho-(CO-CHEt)-Ho, 

Oxybutyric  Acid. 

Ho-(GO-GMez}-Ho, 

Dimethoxalic  Acid. 

Ho-(CO-CHi)-Eto. 

Ethyl-glycollic  Acid. 


468.  Lactic  Acid  is  by  far  the  most  important  member  of 
the  family  to  which  it  gives  name,  and  one  of  the  most  common 
of  the  organic  acids.  It  is  the  acid  of  sour  milk  and  sauer- 
kraut, and  is  a  general  product  of  putrefactive  fermentation. 
The  acid  contained  in  the  gastric  juice  and  many  other  animal 
fluids  is  said  to  be  paralactic  acid.  The  salts  of  lactic  acid  are 
very  numerous,  and  those  of  the  bivalent  metals  bind  two 
atoms  of  the  acid  radicals.  By  the  action  of  HI  lactic  acid 
may  be  converted  into  propionic  acid. 


Ho-(GO-GH-Me)-Ho 

Lactic  Acid.         Ho  _(  cO-GH,-Me)  +-ff,0  +  1-1.  [530] 

Propionic  Acid. 

469.    Monobasic  Acids.    2.  Pyruvic  Series.  —  Two  members 
only  are  well  known  :  — 

Glyoxalic  Acid  Ho-(CO-CO)-H, 

Pyruvic  Acid  Ho  -(CO-  CO}-  Me. 

The  first  may  be  regarded  as  the  semi-aldehyde  of  oxalic  acid, 
a  compound  called  glyoxal  being  the  full  aldehyde,  thus  :  -.  — 

Ho-(GO-GO}-Ho,         Ho-(CO-COYH,        H-(GO-GO)-H. 

Oxalic  Acid.  Glyoxalic  Acid.  Glyoxal. 


512  ALCOHOLS   AND   THEIR   DERIVATIVES.  [§470. 

Both  glyoxalic  acid  and  glyoxal  are  formed  when  common 
alcohol  is  oxidized  by  nitric  acid. 

Ho-(CH2-CHz)  -f  03  =  H-(CO-CO)-H  +  2ff20. 

Alcohol.  Glyoxal. 

[531] 

H-(CO-CO)-H+  0  =  Ho-(CO-CO)-H.       T 

Glyoxal.  Glyoxalic  Acid. 

Glyoxalic  acid  reduces  argentic  oxide  like  an  aldehyde,  and 
passes  into  oxalic  acid. 

Ho-(CO-CO)-H+  0  =  Ho-(00-CO)-Ho.      [532] 

Glyoxalic  Acid.  Oxalic  Acid. 

Compare  (479). 

The  relations  of  these  compounds  to  the  acids  of  the  lactic 
family  are  equally  close. 

ffo-(CO-CO)-H+  IT-IT  =  Ho-(CO-CH.)-Ho. 

Glyoxalic  Acid.  Glycollic  Acid. 

[533] 
Ho-(CO-CO)-Me  +  H-H=.  Ho-(CO-CHMe)-Ho. 

Pyruvic  Acid.  '      Lactic  Acid. 

470.  Dibasic  Acids.  1.  Succinic  Series.  —  Of  this  impor- 
tant series  of  acids,  which  represents  the  second  stage  in  the 
oxidation  of  the  normal  glycols,  the  following  members  are 
known  :  — 

Oxalic  Acid  Ho  -(  CO  -  CO)  -Ho, 

Malonic  Acid  Ho  -(  CO-CH2  C0)-Ho, 

Succinic  Acid  Ho-(CO-( CH2}2CO)-Ho, 

Pyrotartaric  Acid  Ho  -(  CO  -( OH,),-  C0)-Ho, 

Adipic  Acid  Ho-(CO-(CHjfCO)-Ho9 

Pimelic  Acid  Ho  -( CO-(  CH,),-  C0)-ffo, 

Suberic  Acid  Ho -(  OO-(  CH^- CO)- Ho, 

Anchoic  Acid  Ho -(  OO-(  CH2)f  C0)-ffo9 

Sebacic  Acid  Ho-(CO-(  CHs)8-CO)-Ho9 

Roccellic  Acid  ffo-(CO-(CIT2)l5-CO)-ffo. 

With  the  exception  of  the  first,  each  compound  in  the  series 
admits  of  one  or  more  modifications,  the  possible  isomeric 
forms  rapidly  increasing  with  the  number  of  carbon  atoms  in 
the  olefine  radical ;  but  the  exact  constitution  of  these  bodies  has 


§470.]  DIATOMIC   COMPOUNDS.  513 

been  definitely  fixed  in  only  a  few  cases.  The  relation  of  the 
normal  acids  to  the  olefine  radicals,  which  they  are  assumed  to 
contain,  is  indicated  by  the  following  general  synthetical  method, 
by  which  they  may  be  produced  :  — 


Cyanide  of  Radical.  Ko-(CO-(CH,\-CO\Ko  +  2Nff3.    [534] 

Potassic  Salt  of  Dibasic  Acid. 

When,  onj  the  other  hand,  these  acids  are  acted  on  by  agents, 
which  determine  the  elimination  of  C02  from  their  molecules, 
they  are  converted  first  into  monobasic  acids  of  the  acetic 
series,  and  then  into  hydrides  of  the  olefine  radicals.  In  some 
cases  the  action  of  heat  alone  is  sufficient  to  produce  the  result, 
but  in  most  cases  the  body  must  be  heated  with  some  caustic 
alkali  or  earth.  It  will  readily  be  seen  that  by  eliminating  first 
one  and  then  a  second  molecule  of  C0.2  from  the  dibasic  acid, 
the  two  compounds  on  the  same  line  would  be  successively 
formed.  The  name  is  omitted  when  it  is  not  known  that  the 
product  has  been  obtained  by  the  reaction  just  indicated. 

Ho-(CO-CO)-Ho,  ffo-(CO-H),  H-H, 

Oxalic  Acid.  Formic  Acid.  Hydrogen  Gas. 

Ho-(CO-CH2:CO)-Ho,          Ho-(CO-GH&\  Cff4, 

Malonic  Acid.  Acetic  Acid.  Marsh  Gas. 


o,         Ho-(CO-C,H5\ 

Succinic  Acid.  Propionic  Acid. 


Ho-(  C0-C6ff}2-  C0)-Ho,        Ho  - 

Suberic  Acid.  Hexylene  Hydride. 


ffo-(CO-C9ff1?-CO)-Hb,        ffo-(CO-C8ffu), 

Sebacic  Acid.  Octylene  Hydride, 

It  will  thus  be  seen  how  closely  the  acids  of  the  succinic 
series  are  related  to  those  of  the  acetic  series,  and  the  same 
point  is  still  further  illustrated  by  the  following  beautiful  series 
of  reactions  by  which  acetic  acid  has  been  converted  into- 
malonic  acid  and  the  order  of  the  changes  described  above- 
reversed. 

ffo-(CO-CH3)  +  01-01=  ffo-(CO-Cff2Ol)  +  HCl 
ffo-(CO-Cff2Cl)  +KCy  =  KCl+Ho-(CO-CHzCy).  [535] 


22* 


514  ALCOHOLS   AND   THEIR   DERIVATIVES.  [§471. 

In  the  same  way  succinic  acid  has  been  obtained  from 
propionic  acid,  and  formic  acid  may  be  changed  into  oxalic  acid 
still  more  readily. 

ZHo-(CO-H)  -f  2K-0-ff= 

Ko-(CO-CO)-Ko  +  2ff20  +  H-H. 

471.  Succinic  Acid  was  originally  prepared  by  distilling 
amber,  and  takes  its  name  from  the  Latin  name  {succinium) 
of  this  fossil  resin  ;  but  it  is  now  generally  obtained  by  the  fer- 
mentation of  crude  calcic  malate.  It  occurs  ready  formed  in 
amber,  in  certain  lignites,  in  some  varieties  of  turpentine,  and 
in  several  plants.  This  acid  is  a  frequent  product  of  the  oxi- 
dation of  organic  substances,  and  is  always  formed  together 
with  other  products  when  the  fat  acids  are  oxidized  by  nitric 
acid.  Succinic  acid  itself  singularly  resists  the  action  even  of 
powerful  oxidizing  agents.  It  forms,  like  oxalic  acid,  three 
classes  of  salts,  neutral  acid,  and  super  acid.  When  distilled 
it  breaks  up  into  water  and  an  anhydride. 


o  =  0-((CO)2=C2ff4)  +  ff20.  [536] 

Under  the  influence  of  nascent  oxygen  produced  by  electro- 
lysis it  yields  ethylene  carbonic  anhydride  and  water. 

ffo-(CO-C2ffi-CO)-ffo  +  0=  C2ff,  +  2002  +  ff20.  [537] 


472.  Dibasic  Acids.  2.  Fumaric  Series.  —  Two  sets  of 
isomeric  compounds  are  known  corresponding  to  two  terms  of 
a  series  of  acids,  which  stand  in  the  same  relation  to  the  suc- 
cinic series  that  the  acrylic  bears  to  the  acetic.  Thus  we  have 

Fumaric  Maleic  or  Isomaleic  Acids       Ho  -(  CO~O2If2-  CO)-ffo, 
Itaconic  Citraconic  or  Mesaconic  Acids  ffo-(GO-O8IffOO)-ffo. 

The  first  term  admits  of  only  four  modifications,  and  the 
choice  of  symbols  for  fumaric  and  maleic  acids  is  limited  by 
the  fact  that  when  acted  on  by  nascent  hydrogen  they  both 
give  succinic  acid.  Furthermore,  both  acids  combine  directly 
with  two  atoms  of  bromine,  and  though  the  immediate  products 
of  this  union  are  different,  yet  both  bromo  and  isobromo-succinic 
acids,  as  they  are  called,  produce  the  same  succinic  acid  when 
the  bromine  is  replaced  by  hydrogen. 


§473.]  TRIATOMIC   COMPOUNDS/  515 

The  second  term  may  be  varied  in  no  less  than  eleven  dif- 
ferent ways,  and  the  three  formulas  belonging  to  the  three  known 
acids  cannot  at  present  be  recognized. 

These  bodies,  however,  are  related  to  pyrotartaric  acid,  just  as 
the  first  set  are  to  succinic  acid.  All  three  yield  this  product 
when  acted  on  by  nascent  hydrogen,  and  all  three  combine 
with  bromine,  forming  brominated  acids  which  hydrogen  con- 
verts into  the  same  pyrotartaric  acid  as  before. 

Fumaric  and  Maleic  acids  are  both  formed  during  the  distil- 
lation of  malic  acid,  from  which  they  differ  only  by  one  mole- 
cule of  water. 

Ho-(CO-CHfCHHo-CO)-Ho  = 

.  [538] 


Fumaric  or  Maleic  Acid. 

Malic  acid  is  the  acid  principle  of  apples,  and  of  many  other 
fruits.  Fumaric  acid  is  also  found  in  certain  plants,  but 
maleic  acid  has  not  been  met  with  ready  formed  in  nature. 
Itaconic  and  citraconic  acids  are  products  of  the  distillation  of 
citric  acid.  The  third  terms  of  both  groups  are  products  of 
special  processes  which  cannot  be  traced. 

TEIATOMIC   COMPOUNDS. 

473.  Triatomic  Alcohols,  or  Glycerines.  —  Common  glycerine 
is  the  hydrate  of  the  triad  radical  (  O3ff5)=  and  has  all  the  char- 
acteristics of  a  triatomic  alcohol.  The  natural  fats  are  mix- 
tures of  various  salts  of  the  same  radicals  associated  with  acids 
of  the  acetic  or  oleic  groups.  When  boiled  with  alkalies  these 
salts  are  decomposed,  a  hydrate  of  the  radical  (glycerine)  is 
formed,  and  alkaline  salts  of  the  fat  acids  result.  The  last  are 
familiarly  known  as  soaps,  and  such  reactions  are  termed 
saponification.  We  can  also  saponify  the  fats  with  plumbic 
oxide,  and  then  the  lead  soap  (or  "  plaster  ")  being  insoluble  in 
water,  while  the  glycerine  is  soluble,  the  products  are  easily 
separated.  The  fats  may  even  be  saponified  by  water  alone,  if 
acting  at  a  high  temperature,  and  glycerine  is  produced  in  the 
arts  in  large  quantities  by  distilling  the  fats  in  a  current  of 
superheated  steam.  The  products  of  the  decomposition  pass 
over  together ;  but,  in  consequence  of  their  insolubility  and  low 
specific  gravity,  the  fat  acids  separate  from  the  glycerine  in  the 


516  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§473. 

condenser.     The  reaction  in  one  case  is  represented  by  the  fol- 
lowing equation  :  — 


Steorine.  (C.H^O^H,  +  Hf  0^(0^0),.    [538] 

Glycerine.  Stearic  Acid. 

Glycerine,  like  all  the  true  alcohols,  readily  exchanges  JT2  of 
its  radical  for  0  under  the  influence  of  oxidizing  agents,  and 
the  acid  product  is  called  glyceric  acid.  Theory  would  lead 
us  to  expect  two  stages  in  this  process,  and  two  corresponding 
acids,  thus  :  — 


Glycerine. 

(C- 

Glyceric  Acid. 

O- 

Tartrouic  Acid. 

the  first  being  triatomic  and  monobasic  and  the  second  triatoinic 
and  dibasic.  The  second  acid  has  not  as  yet  been  produced 
by  the  direct  oxidation  of  glycerine,  but  there  can  be  little 
doubt  that  tartronic  acid,  which  is  formed  by  the  spontaneous 
decomposition  of  nitro-tartaric  acid,  is  the  acid  in  question. 

When  acted  on  by  HI,  glycerine  is  converted  into  isopropylic 
iodide. 


-I.  [539] 

The  relations  of  glycerine  to  allylic  alcohol  and  pro  py  lie 
glycol  are  illustrated  by  [491  et  seq.~\  and  [514]. 

Under  the  action  of  HOI  glycerine  exchanges  Ho  for  Ol  in 
two  successive  stages,  and  by  means  of  PCl&  all  three  atoms  of 
Ho  may  be  thus  replaced. 


^     (C3ff5y=ci3. 

Glycerine.  Monochlorhydrine.  Dichlorhydrine.  Trichlorhydrine. 

The  compound  (  C3ff5)=Brs  may  be  formed  by  a  similar  re- 
action, and  by  acting  on  this  first  with  argentic  acetate  and  then 
saponifying  the  "  acetine  "  thus  produced,  glycerine  may  be  re- 
generated, When  acted  on  by  a  mixture  of  nitric  and  sul- 
phuric acid  glycerine  yields  a  highly  explosive  compound,  nitro- 
glycerine, which  may  be  regarded  as  a  nitrate  of  glyceryl,  or 
(31). 


§474.]  TRIATOMIC  COMPOUNDS.  517 

Theory  would  lead  us  to  expect  anhydrides  of  glycerine. 
The  first  anhydride  (called  Glycide)  would  have  the  symbol 
(CBff5)=0,ffo,  and  although  this  body  itself  is  not  known,  sev- 
eral of  what  may  be  regarded  as  its  derivatives  have  been 
obtained. 


By  reactions  similar  to  [521  et  seq.~\,  condensed  glycerines 
have  been  formed.     Thus  we  have 


Diglyceric  Alcohol.  Triglyceric  Alcohol. 

which  are  evidently  alcohols  of  higher  atomicity  than  glycerine. 
Like  similar  polybasic  compounds,  they  may  be  regarded  as 
derived  from  a  group  of  two  or  three  molecules  of  glycerine 
by  the  elimination  of  a  sufficient  number  of  atoms  of  water  to 
furnish  the  oxygen  required  to  bind  together  the  basic  radicals 
(151).  Continuing  this  elimination  still  further  we  should 
obtain  a  series  of  anhydrides,  one  of  which  is  known,  viz. 
fHto  and  also  a  corresponding  chlorhydrine 


The  following  reactions  illustrate  the  formation  of  some  of 
the  above  compounds  :  — 

(C3Hs)-=ffo,Cl2  +  K-0-H=  C,ff/0,Cl+H20  +  KCl. 

(  C,ff5}=-0,  Cl  +  HBr  =  (  CzH5YHo,Br,  Cl.       [541] 
(0,ff5)=-0,Cl+KI=  (0^0,1+  KCl 

474.  Ethers  of  Glycerine.  —  By  the  action  of  Na-Q-CJI^ 
upon  mono-,  di-,  and  tri-chlorhydrine,  we  can  replace  either 
one,  two,  or  all  three  of  the  atoms  of  typical  hydrogen  in  gly- 
cerine with  ethyl.  The  products  have  been  called  ethylines. 


By  heating  glycerine  with  acetic  acid  the  typical  atoms  of 
hydrogen  may  be  replaced  by  the  radical  acetyl  in  the  same 
three  proportions  :  — 


**"-          35=- 

Triacetine. 


518  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§475. 

Using  in  a  similar  way  acids  higher  in  the  series,  bodies  similar 
to  the  fats  may  be  produced.  The  natural  oils  and  fats  are 
mixtures  of  such  salts,  chiefly  those  of  palmitic  stearic  and  oleic 
acids.  The  solid  fats  consist  chiefly  of  stearines  and  palmitines, 
and  the  liquid  fats  of  oleines.  The  so-called  drying  oils,  which 
when  exposed  to  the  air  absorb  oxygen  and  change  to  a  dry  resin- 
ous mass,  are  for  the  most  part  "  glycerides  "  of  acids  not  belong- 
ing to  the  acetic  series,  although  closely  related  to  it.  All  gly- 
cerides, when  heated  in  the  air,  are  decomposed  and  yield 
among  other  products  acrolein  whose  penetrating  odor  is 
highly  characteristic.  This  volatile  body  is  formed  abundantly 
when  glycerine  is  heated  with  substances  having  a  strong 
attraction  for  water,  such  as  phosphoric  anhydride,  sulphuric 
acid,  or  still  better  acid  potassic  sulphate. 


(C2ff3CO)-ff.        [542] 

Propylic  alcohol,  propylic  glycol,  and  glycerine  are  all  closely 
related  compounds,  and  may  be  regarded  as  derived  from  the 
same  hydrocarbon, 

C3ff7-JIo=G3ff80,     G,H^Ho,=G,HA     C3ff/ffo3=C3ff8O3, 


and  hence  common  glycerine  is  distinguished  as  propylic  gly- 
cerine. Amylic  glycerine,  the  only  other  compound  of  the 
series  which  has  been  produced,  has  not  been  thoroughly  inves- 
tigated. 

475.    Tribasic  Acid.  —  A  triatomic  acid  of  this  class   has 
been  obtained  from  glycerine  by  the  following  reaction  :  — 

—  SKBr  +  G3H^Cy,. 

[543] 


Glyceryl  Cyanide.  Potassic  Tricarballylate 

The  tricarballylic  acid  may  be  regarded  as  the  third  stage  of 
oxidation  from  an  unknown  hexyl  glycerine,  and  aconitic  acid, 
found  in  the  roots  and  leaves  of  monkshood,  is  the  correspond- 
ing acryloid  compound. 

Acetoid.  Acryloid. 

ffo-GO-C^  Ho-GO-GA 

Butyric  Acid.  Crotonic  Acid. 


lic  Acid.  Aconitic  Acid. 


§476.]  TETRATOMIC  COMPOUNDS.  519 

Aconitic  acid  may  be  obtained  by  cautiously  heating  citric 
acid,  but  at  the  temperature  of  1  60°  it  loses  C02  and  is  con- 
verted into  itaconic  acid,  already  mentioned  among  the  dia- 
tomic compounds. 

(Ho  -  C0)f  Osff3  —  CO,  =  (Ho  -  G0)2=  C3ff4.      [544] 

Aconitic  Acid.  Itaconic  Acid. 

Citric  acid,  the  well-known  acid  principle  of  the  lemon,  but 
which  is  also  found  in  many  other  fruits,  although  only  tribasic, 
is  tetratomic  and  therefore  belongs  to  the  next  division.  It 
differs  from  aconitic  acid  by  only  a  single  molecule  of  water, 


(Ho  -  00)  f  0^-Ho  —  ff20=(ffo-  C0)f  C3ff3,     [545] 

Citric  Acid.  Aconitic  Acid. 

and    hence    the    transformations   which   it   undergoes    when 
heated  (472). 

TETRATOMIC  COMPOUNDS. 

476.  Tetratomic  Alcohol.  —  Erythrite,  a  white  crystalline 
material  extracted  from  various  lichens,  is  regarded  as  an  alco- 
hol of  this  class.  It  combines  with  the  fat  acids,  forming 
ethers,  and  it  contains,  as  the  symbol  given  below  indicates, 
four  atoms  of  typical  hydrogen.  The  following  reaction  ex- 
hibits its  constitution,  and  the  symbols  which  follow  show  its 
relations  to  butylic  alcohol. 

C4ff<?ffo4  -4-  1HI  =<      O4ffs=ffJ     -L  4£Ta0  +  3I-I.  [546] 

Erythrite.  Butylene  lodo-hydride. 


2,          04ffwOs.       C4ffw04. 

Butylic  Hydride.    Butylic  Alcohol.         Butylic  Glycol.       Unknown  Glycerine.       Erythrite. 

Theory  would  lead  us  to  expect  three  acids  from  the  oxida- 
tion of  erythrite,  but  of  these  only  one  is  known.  The  second 
derivative  is  tartaric  acid,  whose  tetratomic  and  dibasic  char- 
acter, already  illustrated  (209),  is  thus  explained  :  — 


v  t       ,243,,,        <==, 

Erythnte.  Unknown.  Tartaric  Acid.  Unknown. 


Citric  acid,  CGH40^04^H,H^  is  a  homologue  of  the  unknown 
third  derivative,  and  may  be  regarded  as  derived  in  the  same 
way  from  an  unknown  alcohol  of  this  series. 


520  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§477. 

Tartaric  acid  is  closely  allied  both  to  malic  and  succmic  acids. 
Malic  acid  is  a  homologue  of  tartaronic  acid,  and  both  have  al- 
ready been  mentioned.  As  the  following  symbols  show,  they 
differ,  each  from  the  next  in  order,  by  a  single  atom  of  oxygen. 

C4ff605,  <74//606, 

or  or      _  or     _ 


Succinic  Acid.  Malic  Acid.  Tartaric  Acid. 

When  tartaric  acid  is  heated  with  HI  it  is  reduced  first  to 
malic  acid,  and  then  to  succinic  acid,  and  on  the  other  hand  by 
treating  bromo-  and  dibromo-  succinic  acids  with  water  and 
argentic  oxide  the  reverse  change  may  be  effected.  The  re- 
markable isomeric  modifications  of  tartaric  acids  have  already 
been  noticed  (70),  (85). 

HEXATOMIC   COMPOUNDS. 

477.  Mannite.  —  No  well-defined  pentatomic  compounds  are 
known,  but  several  hexatomic  compounds  have  been  distin- 
guished, and  it  is  probable  that  many  of  saccharine  bodies  be- 
long to  this  class.  By  extracting  common  manna  (the  ex- 
udation from  several  species  of  ash)  with  boiling  alcohol  we 
easily  obtain  a  highly  crystalline  white  solid,  slightly  sweet  to 
the  taste,  which  is  called  mannite.  This  substance  is  a  hexa- 
tomic alcohol,  and  its  composition  is  represented  by  the  symbol 
C^H^OQ^HQ.  Its  constitution  is  indicate^  by  the  following  cir- 
cumstances :  1.  When  treated  with  a  mixture  of  nitric  and 
sulphuric  acids  it  yields  a  product  similar  to  nitre-glycerine 
CQH^O^(NO^Q.  2.  It  forms  numerous  compounds  with  the 
fat  acids,  in  which,  as  before,  six  atoms  of  hydrogen  are  re- 
placed by  the  acid  radical  ;  for  example,  the  symbol  of  the 
compound  with  stearic  acid  is  (76^I061((718-^50)6.  3.  It  is 
acted  on  by  Him  a  similar  manner  to  erythrite  and  glycerine. 

C»H£ffo9  +  UHI=  CtffjfHZ1  +  Gff20  +  5I-I.  [547] 

4.  By  means  of  oxidizing  agents  mannite  may  be  converted  into 
two  acids,  —  mannitic  acid,  H%WQIC&HQ0,  and  saccharic  acid, 
H6lO&lCQH40^  —  which  bear  the  same  relation  to  this  hexatomic 
alcohol  that  glyceric  and  tartaronic  acids  bear  to  glycerine. 

l  The  products  obtained  in  [539],  [546],  and  [547],  although  isomeric  with 


§478.]  HEXATOMIC  COMPOUNDS.  521 

478.  Saccharine  and  Amylaceous  Bodies.  —  Woody  fibre,  or 
cellulose,  starch,  gum,  and  sugar,  together  with  water,  consti- 
tute the  great  mass  of  all  vegetable  organism,  and  are  the 
materials  on  which  the  animal  chiefly  subsists.  But  although 
these  bodies  play  such  an  important  part  both  in  vegetable  and 
animal  physiology,  we  have  but  little  knowledge  of  their 
chemical  constitution  beyond  their  empirical  formulae.  They 
have  been  divided  into  three  classes,  —  1st.  The  Amyloses,  in- 
cluding woody  fibre,  starch,  and  gum,  all  of  which  are  materials 
incapable  of  crystallization,  and  for  the  most  part  organized. 
2d.  Sucroses,  including  cane  sugar,  sugar  of  milk,  and  the 
sugars  from  different  varieties  of  manna,  which  have  a  crys- 
talline structure,  but  are  not  susceptible  of  direct  fermenta- 
tion. 3d.  Glucoses,  including  grape  sugar  and  fruit  sugar, 
which,  under  the  influence  of  yeast,  break  up  into  alcohol  and 
carbonic  anhydride. 

These  bodies  contain  hydrogen  and  oxygen  in  the  propor- 
tions to  form  water,  and  therefore  have  been  called  the  hy- 
drates of  carbon  ;  but  there  is  no  reason  for  believing  that  the 
atoms  are  grouped  as  this  name  would  indicate.  The  com- 
position of  the  bodies  of  each  class  is  essentially  the  same, 
and  may  be  represented  by  the  following  symbols  :  — 

Amyloses,  C6HIQ05\    Sucroses,  C12ff&0n',    Glucoses,  (76//1206. 

It  is  probable,  however,  that  some  -of  them  ought  to  be  repre- 
sented by  multiples  of  these  formulae,  and  several  of  them 
contain  in  addition  one  or  more  molecules  of  water  of  crys- 
tallization. • 

The  glucoses  have  evidently  the  simplest  molecular  structure 
of  this  class  of  bodies.  They  consist  for  the  most  part  of  two 
isomeric^substances  which  are  most  readily  distinguished  by  the 
action  which  they  exert  when  in  solution  on  the  plane  of  polar- 
ization of  a  ray  of  light.  One  turns  the  plane  to  the  right  and 
the  other  to  the  left  (85),  and  hence  they  have  been  called 

the  iodides  of  the  alcohol  radicals,  are  not  identical  with  them.  If  treated 
with  Ag^O  and  HZ0,  they  are  converted  into  pseudo-alcohols  similar  to  iso- 
propylic  alcohol,  and  their  symbols  may  be  written  on  either  of  the  two  types 
represented  in  the  reactions  just  referred  to.  Thus  we  may  write 


,  ,,     .7 

Hexylene  lodo-hydride.  Iso-hexylic  Iodide. 


522  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§479. 

Dextrose  and  Levulose.  They  are  found  mixed  together  in 
honey,  in  the  juices  of  acid  fruits,  and  in  the  uncrystallizable 
sirups,  called  molasses,  formed  in  the  extraction  of  sugar,  and 
they  may  readily  be  produced  artificially  by  the  action  of  dilute 
acids  and  certain  ferments  on  the  different  varieties  of  starch 
and  sugar.  When  common  starch  is  heated  with  dilute  sul- 
phuric acid,  it  changes  into  dextrose  ;  but  a  variety  of  starch  ex- 
tracted from  the  dahlia-root  changes  under  the  same  conditions 
into  levulose.  Cane-sugar  under  similar  influence  forms  a 
mixture  of  dextrose  and  levulose. 


06.       [548] 

Sucrose.  Dextrose.  •  Levulose. 

The  acid  acts  merely  by  its  presence,  and  remains  unchanged 
during  the  process.  Nitric  acid  oxidizes  glucose  to  saccharic 
or  oxalic  acids  ;  and  under  the  influence  of  nascent  hydrogen 
levulose  changes  to  mannite.  We  may,  therefore,  regard  it  as 
the  aldehyde  of  this  hexatomic  alcohol. 


Mannite.  Levulose.  Mannitic  Acid.  Saccharic  Acid. 

By  the  action  of  nitric  acid  on  milk,  sugar,  or  gum-arabic, 
an  acid  isomeric  with  saccharic  acid  called  mucic  acid  is  formed, 
and  by  the  gentle  action  of  nitric  acid  on  saccharic  acid  tartaric 
acid  may  be  produced. 

All  the  amylaceous  and  saccharine  bodies  form  more  or  less 
stable  compounds  with  strong  bases,  and  most  of  them  when 
treated  with  a  mixture  of  nitric  and  sulphuric  acids  yield  pro- 
ducts similar  to  nitre-glycerine,  of  which  gun-cotton  (31)  is  the 
best  known. 

479.  Glucosides.  —  Under  the  prolonged  influence^  of  heat, 
glucose  has  been  united  with  acetic,  butyric,  stearic,  and 
benzoic  acids,  and  a  class  of  compounds  obtained  similar  to  the 
fats.  The  compound  formed  with  acetic  acid  is  represented  by 
the  symbol  (  G6ff4  05)1(  Czff8  0)6.  These  glucosides  are  interest- 
ing because  the.y  are  probably  allied  to  a  class  of  substances 
found  in  many  plants,  which  under  the  influence  of  ferments 
yield  glucose,  together  with  other  bodies.  The  most  important 
are  :  — 

1.  Amygdaline,  found  in  bitter  almonds,  together  with  an 


§480.]  HEXATOMIC  COMPOUNDS.  523 

albuminous  substance  called  synaptase,  which  when  the  almond 
meats  are  bruised  determines  the  following  reaction  :  — 


=  07ff6  0  +  HGN  +  2  Ofiff12  06.    [549] 

Amygdaline.  Oil  of  Bitter  Glucose. 

Almonds. 

2.  Salicine,  contained  in  the  pith  of  the  willow  and  poplar, 
which  in  presence  of  certain  ferments  is  decomposed  as 
follows  :  — 


r  +  H20  =  07ffsO,  +  Ofiff1206.        [550] 

Salicine.  Saligenine.  Glucose. 

3.  Tannine  or  Tannic  Acid,  widely  diffused  in  the  bark  of 
plants,  and  well  known  for  forming  an  insoluble  compound 
with  gelatine  (as  in  tanning  leather),  and  for  producing  a  black 
color  (ink)  with  ferric  salts.  This  body  when  exposed  in  a 
moist  state  to  the  air,  or  treated  with  dilute  acid,  forms  glucose 
and  gallic  acid. 

CvffaOu  +  ±ff20  =  3  07ff,05  +  06ff,20Q.      [551] 

Tannine.  Gallic  Acid.  Glucose. 

480.  Fermentation.  —  This  term  is  applied  to  a  number  of 
remarkable  chemical  processes,  which  depend  upon  the  life  and 
growth  of  a  very  low  order  of  organized  beings,  belonging 
chiefly  to  the  vegetable  kingdom.  These  organisms  are  the 
efficient  part  of  what  is  called  the  ferment  or  yeast.  The  fer- 
menting material  is  their  appropriate  food,  and  the  products  of 
fermentation  are  in  some  unknown  way  determined  by  the 
vital  process,  different  ferment?,  that  is  different  organisms, 
producing  different  results.  Moreover,  we  can  frequently  dis- 
tinguish between  the  growth  and  propagation  of  these  organisms, 
and  the  normal  vital  process,  by  which  the  products  of  fermen- 
tation are  evolved  ;  the  first  requiring  the  presence  of  certain 
materials,  chiefly  albuminous,  which  otherwise  take  no  part  in 
the  chemical  change.  The  germs  of  these  living  beings  are 
widely  diffused,  floating  even  in  the  atmosphere,  and  begin  at 
once  to  grow  as  soon  as  a  fermentable  liquid  and  the  right 
temperature  supply  the  conditions  of  active  life.  Fermentation, 
therefore,  may  set  in  without  the  apparent  addition  of  any  fer- 
ment, and  on  the  other  hand  the  change  may  be  prevented  by 
sealing  up  the  material  in  air-tight  cans  previously  heated  to 
such  a  temperature  as  will  insure  the  destruction  of  all  living 
germs. 


524  ALCOHOLS  AND  THEIR  DERIVATIVES.  [§481. 

The  principal  modes  of  fermentation  are  :  — 

1.  Alcoholic  fermentation  caused  by  a  fungus,  the  Torvula 
cerevisiae,  commonly  called  yeast,  which  converts  glucose  into 
alcohol  and  carbonic  anhydride,  forming,  however,  at  the  same 
time  a  small  amount  of  succinic  acid  and  glycerine. 

0&ff12  06  =  2  C,ffe  0+2  CO*  [552] 

2.  Acetous  fermentation,  induced  by  the  Mycoderma  vini,  by 
which  alcohol  is  changed  into  vinegar. 

3.  Lactic  fermentation,  in  which  the  Penicillium  glaucum 
converts  saccharine  materials  into  lactic  acid. 


[553] 

Glucose.  Lactic  Acid. 

4.  Butyric  fermentation,  supposed  to  be  caused  by  an  animal, 
in  which  lactic  acid,  formed  as  above,  is  changed  into  butyric 
acid. 

2  C3ffQ  03  =  C4ff8  02  +  2  C02  +  2ff-ff.         [554] 

5.  Mucous  fermentation,  which  sugar  undergoes  under  the 
influence  of  the  "  mucous  ferment,"  giving  rise  to  the  escape 
of  carbonic  anhydride  and  hydrogen,  and  the  formation   of 
mannite,  together  with  a  peculiar  gum  and  a  mucilaginous 
substance. 

481.  Conclusion.  —  The  different  forms  of  fermentation  are 
but  lower  modes  of  the  manifestation  of  that  obscure  power  by 
which  animals  and  plants  not  only  prepare  the  materials  of  their 
tissues,  but  also  secrete  from  their  organisms  the  various  pro- 
ducts of  their  vital  processes.  As  has  been  shown,  we  have 
been  able,  to  a  limited  extent,  to  achieve  in  our  laboratories  the 
same  results,  and  we  can  see  no  limit  to  our  synthetical  meth- 
ods. Nevertheless,  we  have  not  been  able  as  yet  to  produce 
any  of  the  materials  which  make  up  the  great  mass  of  the  tis- 
sues of  all  organized  beings,  and  this,  which  is  true  of  the  gum, 
starch,  and  woody  fibre  of  plants,  is  true  to  a  still  greater  de- 
gree of  such  materials  as  albumen,  caseine,  gelatine,  fibrine,  &c., 
which  are  the  main  constituents  of  the  animal  body.  In  regard 
to  the  composition  of  these  nitrogenized  compounds  we  have  no 
knowledge  except  that  which  may  be  obtained  by  ultimate 


§481.]  HEXATOMIC  COMPOUNDS.  525 

analysis ;  and  although  we  have  every  reason  to  believe  that 
future  investigation  will  reveal  their  molecular  constitution,  so 
far  as  they  are  simple  chemical  compounds,  yet  in  most^  cases 
the  substance  of  these  bodies  cannot  be  isolated  from  the  organic 
structure  which  determines  in  a  great  measure  their  distinctive 
qualities ;  and  not  only  has  man  never  been  able  to  make  the 
simplest  organic  cell,  but  the  whole  process  of  its  growth  and 
development  is  utterly  beyond  the  range  of  his  conceptions. 
Moreover,  even  in  regard  to  those  simpler  products  of  organic 
life  which  we  have  been  able  to  reach  by  synthesis,  we  have  no 
knowledge  of  the  processes  by  which  they  are  formed  in  organic 
nature. 

The  vegetable  kingdom  is  a  great  laboratory,  in  which  the 
sun's  rays  manufacture  from  the  gases  of  the  atmosphere,  and 
from  a  few  earthy  salts  of  the  soil,  the  different  materials  which 
the  organic  builders  employ.  The  animal,  unlike*  the  plant,  has 
not  the  power  of  forming  the  substance  of  its  tissues  from  inor- 
ganic compounds,  but  it  receives  from  the  vegetable  laboratory 
the  materials  required  ready  formed.  It  transmutes  these  pro- 
ducts into  a  thousand  shapes  in  order  to  adapt  them  to  its  wants ; 
but  its  peculiar  province  is  to  assimilate  and  consume,  not  to 
produce.  The  nitrogenized  compounds  just  referred  to  are  the 
portion  of  its  food  which  supplies  the  constant  waste  attending 
all  the  vital  processes.  The  non-nitrogenized  starch  and  sugar, 
although  they  form  the  greater  part  of  our  food,  are  never  incor- 
porated into  the  tissues  of  the  body,  but  are  merely  the  fuel  by 
which  its  temperature  is  maintained.  Here,  however,  chem- 
istry stops,  and  the  science  of  physiology  begins. 

In  closing  this  summary  of  facts,  we  must  remind  the  student 
that,  as  we  stated  in  the  introduction,  we  have  made  no  attempt 
at  completeness.  Although  the  chief  characteristics  of  all  the 
chemical  elements  have  been  illustrated,  yet  important  classes 
of  compounds  have  been  necessarily  left  unnoticed,  and  this  is 
especially  true  in  the  last  division  of  the  book.  Organic  chem- 
istry presents  such  a  vast  array  of  facts  that  the  attempt  to 
comprehend  the  whole  field  would  simply  lead  to  confusion,  and 
serve  no  useful  end.  We  have,  therefore,  limited  our  scope  to 
those  classes  of  compounds  whose  molecular  structure  is  well 
understood,  and  our  great  object  has  been  to  illustrate  the 
methods  by  which  a  knowledge  of  this  structure  has  been 


526  QUESTIONS  AND  PROBLEMS.  [§481. 

reached.  It  is  by  these  methods  that  the  new  philosophy  of 
chemistry  is  chiefly  distinguished  from  the  old,  and  to  them  we 
shall  especially  direct  the  student's  attention  in  the  questions 
which  follow.  He  should  not  content  himself,  however,  with 
simply  answering  these  questions,  but,  by  an  exhaustive  study 
of  all  the*  reactions  which  have  been  given,  and  by  a  constant 
use  of  graphic  symbols,  endeavor  to  become  imbued  with  the 
spirit  of  the  philosophy  which  it  has  been  the  object  of  this 
book  to  illustrate. 


Questions  and  Problems. 
Carbon  and  Oxygen. 

1.  Deduce  the  atomic  weight  of  carbon,  and  state  the  facts  and 
principles  on  which  the  conclusion  is  based. 

2.  When  the  product  of  the  combustion  of  coal  is  CO,  what  pro- 
portion of  the  calorific  power  of  the  fuel  is  lost  ?     (61). 

3.  Is  the  combination  of  C02  with  additional  carbon  in  passing 
through  a  mass  of  incandescent  coal  attended  with  an  evolution  or 
an  absorption  of  heat  ?    Estimate  the  amount  of  the  effect  pro- 
duced. 

4.  Illustrate  by  examples  and  seek  to  establish  by  reactions  or 
other  facts  the  oxatyl  theory  of  the  constitution  of  organic  acids. 

Carbon  and  Nitrogen. 

5.  On  what  facts  is  the  symbol  of  cyanogen  gas  based  ? 

6.  In  what  respects  does  HCy  resemble,  and  how  does  it  differ, 
from  the  hydrogen  acids  of  the  chlorine  group  ? 

7.  What  is  the  distinction  between  the  two  classes  of  double 
metallic  cyanides? 

8.  Represent  by  graphic  symbols  the  constitution  of  several  of  the 
polymeric  compounds  of  cyanogen,  including  the  ferro  and  ferri- 
cyanides  of  potassium. 

9.  What  proof  is  furnished  by  the  reactions  of  (425)  that  the 
amine  and  amide  compounds,  there  mentioned,  have  the  constitution 
represented  by  the  symbols  assigned  to  them  ? 

10.  Repeat  the  reactions  given  in  (425),  writing  the  symbol  of 
cyanic  ether  after  the  ammonia  type. 

11.  Represent  by  graphic  symbols   the   constitution  of  cyanic 


QUESTIONS  AND  PROBLEMS.  527 

ether  and  cyanetholine  respectively,  and  give  the  reactions  from 
which  the  symbols  are  deduced. 

1 2.  Urea,  when  in  solution  m  water,  changes  into  ammonic  car- 
bonate.    Write  the  reaction. 

Carbon  and  Hydrogen. 

13.  How  many  essentially  different  modes  of  grouping  are  possi- 
ble with  a  carbon  skeleton  of  four  atoms,  assuming  that  no  atom  is 
united  to  any  one  of  its  neighbors  by  more  than  one  of  its  affinities  ? 
How  many  with  a  skeleton  of  five  atoms,  &c.  ? 

14.  Make  a  table  of  the  possible  hydrocarbons  in  series  of  homo- 
logues  and  isologues. 

15.  How  many  essentially  different  modes  of  grouping  are  possi- 
ble with  the  compounds  C6HW  C6Hlz,  and  C6H0  ? 

16.  Is  the  number  of  H  atoms  in  the  molecule  of  a  hydrocarbon 
necessarily  an  even  number  ? 

17.  Is  any  evidence  given  of  the  synthesis  of  marsh  gas  ? 

18.  Why  may  the  three  expressions  C2H&-C2H&,  C&H7-CH3  and 
C^Hlo  represent  identical  compounds  ? 

19.  Explain  the  manner  in  which  the  successive  hydrogen  atoms 
of  C^HI  may  be  replaced  by  bromine. 

20.  Write   the   symbols  of   the  different  hydrocarbons   of   the 
phenyl  series  on  the  assumption  that  they  all  contain  the  radical 
C6H&  united  to  the  radicals  of  the  methyl  series,  and  show  how  many 
isomeric  modifications  are  possible  in  each  case. 

21.  Describe  the  method  of  preparing  aniline  from  benzol. 

22.  Show  by  graphic  symbols  the  relations  of  the  radicals  allyl 
and  glyceryl. 

23.  Illustrate  by  graphic  symbols  the  relations  of  the  oxygenated 
to  the  simple  hydrocarbon  radicals,  and  explain  the  principle  stated 
in  (436). 

Monatomic  Alcohols,  Sfc.    Marsh  Gas  Series. 

24.  Represent  graphically  the  constitution  of  the  alcohols  of  the 
marsh  gas  series,  and  show  that  the  reactions  of  (438)  sustain  your 
theory. 

25.  Write  a  series  of  reactions  by  which  the  synthesis  of  propylic 
alcohol  can  be  effected,  starting  with  mineral  substances. 

26.  Analyze  reactions  [438]  and  [439],  and  trace  the  action  of 
nascent  hydrogen  and  N203  in  these  cases  as  illustrating  their  use 
as  reagents  in  organic  chemistry. 


QUESTIONS  AND  PROBLEMS. 

27.  What  general  method  of  preparing  the  amines  (167)  is  indi- 
cated by  [438] ? 

28.  Show  that  the  constitution  of  acetic  acid  may  be  deduced 
from  [374],  [443],  [448],  and  [449]. 

29.  Write  a  series  of  reactions  by  which  acetic  acid  may  be 
converted  into  propionic  acid. 

30.  What  is  the  use  of  P206  as  a  reagent  in  organic  chemistry 
[445] ? 

31.  Analyze  reaction  [444]  and  show  what  an  important  effect 
can  be  produced  by  the  action  of  potassic  hydrate  on  the  cyanide 
of  a  hydrocarbon  radical.     Compare  [389]. 

32.  What  conclusions  would  you  deduce  from  reactions  [450]  to 
[452]  in  regard  to  the  constitution  of  the  fat  acids  ?     Illustrate  by 
developing  in  full  the  rational  formula  of  butyric  acid. 

33.  What  are  the  several  sources  of  palmitic  acid  ? 

34.  Compare  the  constitution  of  iso-butyric  and  iso  valeric  acids 
obtained  by  [456]  and  [457]  with  the  normal  compounds.     Are 
other  isomers  possible  ? 

35.  Write  the  reactions  by  which  methylic  ether  is  prepared. 

86.  Explain  the  process  of  etherification  as  illustrated  by  [458] 
and  [459].     What  is  the  essential  difference  of  conditions  in  the 
two  reactions  ? 

87.  Write  the  reactions  by  which  common  ether  may  be  obtained 
after  [461]. 

38.  Make  a  table  of  the  different  ethers. 

39.  All  the  hydrogen  atoms  of  methylic  ether  may  be  replaced 
by  chlorine  in  successive  pairs.     Write  the  symbols  of  the  compounds 
thus  formed. 

40.  Analyze  reactions  [461]  as  illustrating  the  use  of  sodium  as  a 
reagent  in  organic  chemistry. 

41.  Describe  the  methods  of  preparing  the  compound  ethers,  and 
compare  them  with  the  reactions  by  which  mineral  salts  are  ob- 
tained. 

42.  Show  in  what  way  the  presence  of  a  strong  acid  assists  the 
reactions  expressed  by  [466]  and  [467]. 

43.  To  what  does  saponification  correspond  in  mineral  chemistry  ? 

44.  Write  the  reaction  of  water  on  acetic  ether. 

45.  Write  the  reaction  by  which  butyric  anhydride  may  be  pre- 
pared. 


QUESTIONS  AND  PROBLEMS.  529 

46.  Write  the  reaction  of  water  on  acetic  anhydride. 

47.  Compare  the  effects  of  PC13  and  PCl&  when  used  as  reagents 
in  organic  chemistry,  so  far  as  illustrated  by  [471]  and  [34]. 

48.  In  what  manner  may  the  haloid  ethers  be  converted  into 
amines  ? 

49.  Chloroform  may  be  regarded  as  the  chloride  of  the  trivalent 
radical  CH.     Do  you  know  of  any  reaction  which  illustrates  this 
point ? 

50.  Analyze  the  reactions  by  which  the  aldehydes  are  formed, 
and  show  how  far  they  indicate  the  constitution  of  these  bodies. 

51.  Write  the  reaction  which  takes  place  when  the  aldehydes  are 
heated  with  potassic  hydrate. 

52.  Represent  by  graphic  symbols  the  constitution  of  the  alde- 
hydes and  ketones,  and  show  that  the  chemical  relations  of  the  two 
classes  of  isomeric  compounds  are  the  result  of  a  difference  of  atomic 
grouping.     Show  also  that  your  theory  of  the  constitution  of  these 
bodies  is  a  legitimate  inference  from  the  reactions,  of  which  they 
are  susceptible. 

53.  Illustrate  by  graphic   symbols   the   difference   between  the 
pseudo-alcohols  and  the  normal  compounds  and  the  relations  in  which 
they  stand  to  the  ketones  and  aldehydes  respectively.     Show  that 
the  symbols  assigned  to  the  normal  and  secondary  alcohols  are  le- 
gitimately deduced. 

54.  Compare  by  the  graphic  method  the  constitution  of  the  three 
classes  of  alcohols.     Take  heptyl  alcohol  with  its  isomers  as  an  ex- 
ample, and  point  out  the  differences  in  the  carbon  skeletons  of  these 
isomeric  compounds.     In  what  does  a  normal  alcohol  consist  ? 

55.  Make  a  table  exhibiting  the  relations  of  the  different  com- 
pounds of  the  marsh  gas  series  including  hydrocarbons,  alcohols, 
acids,  aldehydes,  acetones,  and  ethers. 

Vinyl  Series. 

56.  The  differences  between  the  vinylic  and  ethylic  alcohols  may 
be  referred  to  what  differences  in  t^ie  structure  of  the  carbon  skele- 
ton of  these  two  classes  of  compounds  ?     What  proof  have  you 
that  such  a  difference  exists  ? 

57.  Compare   by   the   graphic   method   the   difference   between 
vinylic  alcohol,  acetic  aldehyde,  and  ethylenic  oxide,  and  give  the 
reasons  for  your  mode  of  grouping  the  atoms. 

58.  Why  should  you  not  expect  to  obtain  an  acid  from  vinylic 

25  HH 


530  QUESTIONS  AND  PKOBLEMS. 

alcohol  by  the  action  of  oxidizing  agents,  when  allylic  alcohol  yields 
both  an  aldehyde  and  an  acid  ? 

59.  Write  the  reaction  by  which  ally  lie  alcohol  is  converted  into 
acrolein  and  acrylic  acid. 

60.  How  far  is  the  change  from  glycerine  into  acrolein  attended 
with  a  change  of  type  V 

61.  In  what  does  the  difference  between  the  structure  of  the 
acids  of  the  acrylic  and  acetic  series  consist  ? 

62.  Carefully  analyze  the  reactions  by  which  different  types  of 
structure  in  the  acrylic  series  have  been  obtained,  and  show  that  the 
conclusions  reached  are  legitimate. 

63.  How  and  under  what  conditions  does  PC13  act  as  a  dehy- 
drating agent  ? 

64.  In  what  way  does  [444]  and  [505]  indicate  the  structure  of 
|3  crotonic  acid  ? 

65.  Give  the  general  symbols  of  the  three  classes  of  acryloid 
acids. 

Phenyl  Series. 

66.  Represent  the  constitution  of  benzoic   alcohol   by  graphic 
symbols,  and  show  how  far  its  structure  resembles  that  of  the  alco- 
hol of  the  ethylic  series  containing  the  same  number  of  carbon 
atoms.     Compare  the  carbon  skeletons  of  the  two  compounds. 

67.  Why  is  it  that  carbolic  acid,  although  homologous  with  benzoic 
alcohol,  differs  from  it  so  greatly  in  its  chemical  relations  ? 

68.  How  is  toluol  related  to  benzol,  and  by  what  series  of  reac- 
tions may  the  first  be  changed  into  the  last  ? 

69.  How  is  cressylic  alcohol  related  to  carbolic  acid  ?     Represent 
with  graphic  symbols  the  structure  of  the  two  bodies. 

70.  Write  the  reaction  by  which  benzoic  acid  is  produced  from 
hippuric  acid  (168). 

71.  Represent  graphically  the  relations  of  cinnamic  to  benzoic 
acid,  and  point  out  the  difference  of  structure  in  the  carbon  skele- 
ton of  the  two  compounds.     Wh*t  similar  relations  have  previously 
been  noticed  ? 

72.  Represent  graphically  the  relations  of  salicylic  acid  to  ben- 
zoic acids.     What  acid  stands  in  a  similar  relation  to  acetic  acid  ? 

73.  Make  a  table  exhibiting  the  relations  of  the  different  com- 
pounds of  the  radical  phenyl,  with  their  possible  homologues,  and 
show  how  far  the  reactions,  which  have  been  given,  indicate  their 
molecular  structure. 


QUESTIONS  AND  PROBLEMS.  531 

Diatomic  Alcohols,  &c. 

74.  Describe  the  several  processes  by  which  the  glycols  may  be 
produced. 

75.  Illustrate  by  graphic  symbols  the  constitution  and  relations  of 
the  different  derivatives  of  ethylic  glycol,  especially  of  the  chlorhy- 
drines,  bromhydrines,  &c. 

76.  Point  out  the  differences  between  the  chemical  relations  of 
ethylic  oxide  (common  ether)  and  ethylenic  oxide,  and  show  how  far 
they  may  be  explained  by  differences  of  structure. 

77.  Describe  the  reactions,  by  which  condensed  glycols  may  be 
produced,  and  cite  examples  of  similar  compounds  from  the  mineral 
kingdom.      What  proof  is  there  that  these  compounds  have  the 
structure  assigned  to  them,  and  why  can  greater  certainty  be  reached 
in  regard  to  the  structure  of  these  bodies  than  in  regard  to  that  of 
the  mineral  products  they  are  said  to  explain  ? 

78.  Illustrate  by  graphic  symbols  the  structure  of  the  three  chief 
classes  of  acids  of  the  lactic  family,  and  show  in  each  case  how  the 
conclusion  has  been  reached. 

79.  Construct  the  graphic  symbols  of  ethylene  and  ethylidene, 
and  give  the  reasons  for  the  forms  adopted. 

80.  Show  that  the  constitution  of  the  known  glycols  can  be 
inferred  from  that  of  the  acids  of  the  lactic  family. 

81.  What  is  meant  by  an  olefine  acid  ?     In  what  way  must  the 
carbon  atoms  in  the  olefines  be  arranged  ?     Show  that  the  conclu- 
sion is  trustworthy. 

82.  Compare  the  reaction  of  potassic  hydrate  on  cyanhydrine  of 
ethylene  and  on  cyanhydrine  of  ethylidene.     Can  you  draw  any 
legitimate  inference  in  these  cases  as  to  the  structure  of  the  result- 
ing compounds  ? 

83.  Explain  the  term  etheric  acids.     Has  any  example  of  such 
compounds  been  previously  given  ? 

84.  Represent  by  graphic  symbols  the  constitution  of  the  isomeric 
compounds  cited  in  (467),  and  inquire  whether  further  variations 
are  possible. 

85.  Write  the  reactions,  1.  of  lactic  acid  on  sodic  carbonate,  2. 
of  sodium  on  sodic  lactate,  3.  of  ethylic  iodide  on  disodic  lactate. 

86.  What  is  the  general  action  of  HI  as  a  reagent  in  organic 
chemistry  ?     [530.] 

87.  Write  the  reaction  of  potassic  hydrate  on  cyanide  of  ethylene, 
and  show  how  far  this  establishes  the  constitution  of  succinic  acid. 


532  QUESTIONS  AND  PKOBLEMS. 

88.  Write  the  reaction  which  takes  place  when  one  molecule  of 
CO2  is  eliminated  from  malonic  acid  by  the  action  of  heat,  or  when 
succinic  acid  is  decomposed  in  a  similar  way  if  heated  with  lime. 

89.  Write  the  reaction  when  suberic  acid  is  heated  with  excess 
of  baryta. 

90.  What  is  the  general  action  of  lime  or  baryta  when  heated 
with  an  organic  acid  ? 

91.  Show  by  graphic  symbols  how  the  acids  of  the  succinic  series 
are  related  to  those  of  the  acetic  series,  and  describe  the  methods 
by  which  one  class  of  compounds  may  be  converted  into  the  other. 

92.  Show  that  reactions  [536]  and  [537]  confirm  the  conclusion 
already  reached  in  regard  to  the  constitution  of  succinic  acid. 

93.  In  what  isomeric  form  may  the  symbol  of  succinic  acid  be 
written,  and  what  radical  would  it  then  contain,  in  place  of  ethy- 
lene  ?     What  proof  have  you  that  it  does  contain  ethylene  ? 

94.  Succinic  acid  is  formed  when  butyric  acid  is  oxidized  (by 
nitric  acid).     Write  the  reaction. 

95.  Write  the  general  symbols  of  the  three  classes  of  the  succi- 
nates  both  of  univalent  and  bivalent  radicals. 

96.  What  is  the  characteristic  of  an  acryloid  acid  ?     Show  that 
fumaric  acid  conforms  to  this  type. 

97.  Show  by  graphic  symbols  the  possible  forms  of  the  first  term 
of  the  fumaric  series. 

98.  Show  how  far  the  fact  that  both  fumaric  and  maleic  acids 
yield  succinic  acid,  under  the  influence  of  nascent  hydrogen,  fixes 
their  symbols.     Show  also  that  the  brominated  compounds  may  be 
different;  while  the  further  products   obtained  by  the  action  of 
nascent  hydrogen  on  the  last  may  be  identical. 

99.  Represent  graphically  some   of  the  possible  forms  of  the 
second  term  of  the  fumaric  series,  and  trace  the  relations  of  these 
compounds  to  pyrotartaric  acid. 

100.  Compare  the  graphic  symbols  of  succinic,  fumaric,  and  malic 
acids. 

Triatomic  Compounds. 

101.  Write  the  reaction  on  stearine,    1.  of  solution  of  potassic 
hydrate,  2.  of  plumbic  oxide  and  water,  3.  of  superheated  steam. 

102.  Compare  the  graphic  symbols  of  glycerine,  glyceric  acid, 
and  tartaronic  acid,  and  explain  their  atomic  and  basic  relations. 


QUESTIONS  AND  PROBLEMS.  533 

103.  How  far  do  the  reactions  [514]  and  [539]  indicate  the 
construction  of  the  basic  radical  of  glycerine  ? 

104.  Write  the  reaction  by  which  the  several  chlorhydrines  of 
glycerine  are  obtained,  and  point  out  their  relations  to  the  triatomic 
character  of  the  compound. 

105.  Compare  the  anhydrides  of  glycerine  with  the  polybasic 
mineral  compounds. 

106.  Give  the  symbols  of  the  three  stearines  and  the  three  oleines 
corresponding  to  the  three  acetines. 

107.  Exhibit  by  graphic  symbols  the  relations  of  glycerine  to 
acrolein. 

108.  Compare  graphically  the  relations  of  propylic  alcohol,  pro- 
pylic  glycol,  and  glycerine. 

109.  A  normal  alcohol  may  be  converted  into  an  acid  either  by 
oxidation  or  by  a  reaction  similar  to  [543];  compare  the  results 
obtained,  and  show  the  bearing  of  the  facts  on  the  oxatyl  theory  of 
organic  acids. 

110.  Write  the  symbols  of  the  different  acids  which  might  theo- 
retically be  formed  by  the  oxidation  of  the  assumed  hexyl  glycerine. 

Ill     Compare  the  graphic  symbols  of  trie arbally lie  and  aconitic 
acids. 

112.  Compare  the  graphic  symbols  of  citric,  aconitic,  and  itaconic 
acids,  and  explain  the  change  of  the  first  into  the  last  through  the 
second. 

Tetratomic  Alcohols,  &c. 

113.  Make  a  table  exhibiting  the  relations  of  tartaric  and  citric 
acids  to  the  tetratomic  alcohols. 

114.  When  tartaric  acid  is  reduced  by  HI,  it  changes  first  into 
malic  and  then  into  succinic  acid.     Write  the  reactions  and  inquire 
how  far  they  aid  in  establishing  the  constitution  of  the  bodies  in- 
volved. 

115.  Compare  the  carbon  skeletons  of  one  or  more  of  each  of 
the  classes  of  acids  which  have  been  studied,  and  show  that  the 
variations  are  limited  to  a  few  principal  types.     Then,  by  attaching 
atoms  of  H,  Ho,  NHt,  COHo  or  O  to  these  skeletons,  illustrate  the 
relations  of  the  various  classes  of  compounds  which  may  be  formed 
around  a  common  nucleus. 


CHAPTER    XX. 

APPENDIX. 

Complex  Amines. 

482.  Aniline  Colors.  —  These  beautiful  products  of  modern 
chemistry,  which  are  so  highly  valued  on  account  of  their  bril- 
liant hues  and  wonderful  tinctorial  power,  belong  to  the  class 
of  compounds  called  amines,  whose  chemical  relations  have 
been  already  described  (167).  They  are,  so  far  as  known, 
highly  complex  bodies  of  the  ammonia  type,  and  will  serve  to  ex- 
tend our  knowledge  of  this  class  of  compounds,  connecting  them 
with  the  compounds  of  the  hydro-carbon  radicals,  with  which 
we  have  become  more  recently  acquainted.  The  processes  by 
which  the  aniline  dyes  are  prepared  in  the  arts  consist  chiefly 
in  the  oxidation  of  a  mixture  of  aniline  and  toluidine,  but  the 
precise  reactions  involved  can  seldom  be  traced.  Nevertheless 
we  have  been  able  to  reach  a  general  knowledge  of  their  con- 
stitution, although  it  must  be  held  subject  to  revision  by  the 
results  of  the  ever-widening  investigations,  which  the  great 
interest  of  these  beautiful  bodies  invites. 

The  process  by  which  aniline  is  obtained  from  benzol  has 
been  already  described,  and  toluidine  is  prepared  in  precisely 
the  same  way  from  toluol  (434).  By  the  action  of  oxidizing 
agents  on  these  monamines  we  can  obtain  four  distinct  triamine 
bases,  whose  salts  are  all  deeply  colored.  Each  molecule  of  the 
monamine  loses  by  oxidation  two  atoms  of  hydrogen,  and  then 
three  of  these  dehydrated  molecules  coalesce  to  form  one  mole- 
cule of  the  complex  triamine,  thus  : — 


Aniline.  Violaniline. 

7HfN=H,  —  Qff=  QuH^Nf 

Aniline.  Toluidine.  Mauvaniline. 

7ff7-fcff2  —  £ff=  Cvff^Nf 

Toluidine.  Kosaniline 


Toluidiue.  Cnrysotoluidine. 


§482.]  ANILINE  COLORS.  535 

The  simplest  conception  we  can  form  of  the  constitution  of 
these  products  is  indicated  below  :  — 


NH   NH  NH   NH 


iolaniline.  Mauvaniline. 


NH   NH  NH   NH 


Kosanlline.  Chrysotoluidine. 

and  it  can  easily  be  seen  that  such  a  grouping  might  readily 
result,  if  we  assume  that  of  the  two  atoms  of  hydrogen  which 
each  molecule  of  the  monamine  loses,  one  is  torn  from  the  ni- 
trogen atom  and  the  other  from  the  benzol  nucleus.  All  we 
know,  however,  with  any  certainty,  is  that  there  remain  three 
atoms  of  typical  hydrogen,  which  may  be  further  replaced  by 
various  hydro-carbon  radicals,  and  this  is  expressed  by  the  first 
set  of  symbols. 

Of  these  bases  rosaniline  is  practically  the  most  important. 
The  usual  process  by  which  its  compounds  are  manufactured 
in  the  arts  consists  of  three  stages  :  first,  the  conversion  of 
benzol  and  toluol  (obtained  from  coal-tar  naphtha  by  fractional 
distillation)  into  nitro-beuzol  and  nitro-toluol  (434)  ;  second,  the 
reduction  of  these  nitro-compounds  (usually  by  mixing  them 
with  acetic  acid  and  iron-turnings)  to  aniline  and  toluidine 
[428]  ;  third,  the  oxidation  of  a  mixture  of  these  bases,  in 
about  the  proportions  of  one  of  aniline  to  two  of  toluidine,  by 
means  of  arsenic  acid.  To  this  end  the  mixture  is  treated  with 
a  concentrated  sirupy  solution  of  the  reagent,  and  the  whole 
mass  is  heated  to  about  150°,  and  kept  at  this  temperature  un- 
der constant  stirring  for  several  hours.  The  crude  product, 
a  resinous  solid  with  a  bronze-like  lustre,  is  dissolved  in  boiling 
water,  and  a  large  excess  of  sodic  chloride  added,  which  precipi- 
tates chloride  of  rosaniline  in  crystals,  that  reflect  beautiful  chang- 
ing green  hues  like  beetles'  wings,  but  are  red  by  transmitted 
light,  and  yield  with  alcohol  or  acetic  acid  deep  red  solutions. 
From  the  chloride  the  other  salts  of  the  same  base  may  be  readily 
prepared,  including  the  hydrate,  C^H^N^  .  ZH^O,  which  falls  as  a 


536  ANILINE  COLORS.  [§482. 

brownish-yellow  precipitate  on  adding  caustic  soda  or  ammonia 
to  a  solution  of  any  of  the  aniline  reds  of  commerce,  but  when 
purified  it  is  colorless,  becoming,  however,  rose-red  on  exposure 
to  any  acid,  even  the  carbonic  acid  of  the  atmosphere.  It  is 
a  singular  fact  in  regard  to  all  the  bases  mentioned  above,  that, 
while  all  their  salts  are  such  powerful  pigments,  they  are  them- 
selves colorless.  The  hydrate  of  rosaniline  is  insoluble  in  ether 
or  coal-tar,  nearly  so  in  water,  only  slightly  soluble  in  aqua 
ammonia,  but  dissolves  with  readiness  in  alcohol,  with  which  it 
forms  deep  red  solutions.  With  acids  it  forms  three  classes  of 
salts,  neutral,  acid,  and  di-acid,  which  crystallize  readily.  It  is 
the  last  of  these  which  are  so  remarkable  for  their  beetle-like 
lustre  and  give  such  beautiful  rose-red  solutions.,  and  they  are 
the  true  coloring  compounds.  A  great  variety  of  these,  in- 
cluding besides  the  arseniate  the  chloride,  nitrate,  sulphate,  chro- 
mate,  acetate,  oxalate,  and  tannate,  are  used  in  the  arts  and 
known  under  fanciful  names,  such  as  magenta,  azaliene,  fuch- 
sine,  roseine,  &c.  They  are  most  of  them  freely  soluble  in 
water  and  alcohol,  but  the  tannate  is  so  insoluble  that  it  is  used 
for  fixing  the  color  upon  calico  and  recovering  the  dye  from 
nearly  spent  solutions. 

It  was  discovered  by  Hofmann  that  the  three  atoms  of  typical 
hydrogen  remaining  in  rosaniline  may  be  replaced  by  the  hy- 
dro-carbon radicals,  and  these  replacements  give  rise  to  beau- 
tiful violet  and  blue  pigments.  The  so-called  Hofmann's  violets 
and  blues  are  salts  of  mono,  di,  or  tri  pheuylic,  ethylic,  or  me- 
thylic  rosaniline  ;  and  the  further  the  substitution  is  carried,  the 
more  do  the  blue  tints  preponderate  in  the  resulting  dye.  The 
phenylic  compounds  are  obtained  by  heating  the  salts  of  rosani- 
line with  aniline  under  pressure,  and  the  ethylic  or  methylic 
compounds  may  be  prepared  by  treating  the  rosaniline  salts 
with  the  iodides  or  bromides  of  ethyl  or  methyl. 

Besides  the  definite  compounds,  whose  chemical  relations 
have  been  described  above,  there  are  prepared  in  the  arts  a 
very  great  variety  of  other  aniline  dyes,  including  greens,  yel- 
lows, blacks,  and  indeed  almost  every  color.  They  are  all 
probably  compounds  of  one  of  the  four  bases  described  above, 
or  of  analogous  bases  derived  from  them,  but  they  are  fre- 
quently mixtures,  and  from  the  empirical  processes  by  which 
they  are  prepared  we  can  draw  no  definite  conclusion  as  to 
their  precise  constitution. 


§  483.]  UREA.  537 


Complex  Amides. 

483.  Urea  N2ff4CO. — This  compound  has  already  been 
mentioned  as  an  example  of  a  diamide  (168),  and  its  synthesis 
by  the  transformation  of  ammonic  cyanate  has  been  explained 
[404].  It  is  a  substance  of  very  great  physiological  interest. 
It  has  been  found  in  several  of  the  fluids  of  the  animal  body, 
and  forms  a  large  constituent  of  the  vitreous  humor  of  the  eye. 
With  all  the  higher  animals  it  is  the  final  product  of  the  oxida- 
tion of  their  tissues,  and  the  chief  form  in  which  they  are  elim- 
inated from  the  body  after  having  discharged  the  functions  of 
life.  It  takes  its  name  from  the  secretion  of  the  kidneys,  of 
whose  solid  constituents  it  forms  by  far  the  largest  part,  and 
after  being  voided  by  the  body  it  is  soon  converted  into  car- 
bonic dioxide  and  ammonia,  the  two  substances  which,  together 
with  water,  are  the  principal  food  of  the  vegetable  world  (481) 
(64).  This  change  is  apparently  induced  by  certain  highly 
unstable  bodies,  with  which  urea  is  associated  in  the  urine,  and 
consists  simply  in  the  assimilation  of  one  molecule  of  water  to 
each  molecule  of  urea,  thus :  — 

Nzff4CO  +  ff20  =  2Nffs  +  C02.  [555] 

The  same  change  may  be  produced  by  strong  sulphuric  acid 
and  by  various  alkaline  reagents,  also  by  heating  with  water 
alone  in  sealed  tubes  to  temperatures  above  the  boiling  point. 

Urea  acts  as  a  feeble  base,  forming  salts  with  the  stronger 
acids,  and  of  these  the  nitrate,  (N2H^CO)HNO^  and  the  oxa- 
late,  (N2ff4CO)2H2O20^  are  the  most  readily  crystallized.  It 
also  forms  definite  compounds  with  several  metallic  oxides  and 
with  many  salts.  In  all  these  cases  there  is  no  replacement 
of  the  hydrogen  atoms  of  the  urea ;  but  its  molecules  combine 
directly  with  those  of  the  acid,  oxide,  or  salt,  as  in  the  above 
examples.  Such  a  reaction  as  this,  however,  is  a  characteristic 
of  an  amine  (167),  and  not  what  we  should  anticipate  of  the 
neutral  amide  of  carbonic  acid,  whose  acid  amide  forms  the 
well-known  ammonic  carbamate  (168)  and  (174).  But,  un- 
like a  true  diamine,  one  molecule  of  urea  does  not  neutralize 
two  molecules  of  a  monobasic  acid,  but  only  one,  as  in  the 
above  examples.  Hence  some  chemists  do  not  regard  urea  as 
the  true  carbamide,  but  only  a  compound  isomeric  with  it,  and 


538  COMPOUND  UREAS.  [§484. 

the  following  formulae  represent  possible  views  of  its  constitu- 
tion :  — 


Ammonic  Cyanate.  Carbamide.  Urea  ?  Urea  ? 

Against  each  of  these,  however,  we  might  urge  plausible  ob- 
jections, and  the  simple  carbamide  formula,  which  is  here 
adopted  as  a  provisional  mode  of  explaining  the  relations  of 
the  compound,  is  not  less  probable  than  either  of  the  others. 

In  whatever  way  we  may  write  the  symbol  of  the  urea  mole- 
cule, its  single  carbon  atom  must  be  directly  united  to  one  or 
both  of  the  two  nitrogen  atoms  with  which  it  is  associated. 
Hence  arises  an  intimate  relationship  between  urea  and  the 
compounds  of  cyanogen,  from  which  it  is  so  readily  derived. 
Urea,  when  heated  under  regulated  conditions,  yields  besides 
other  products  both  cyanic  and  cynnuric  acids,  thus  :  — 


3  =  Ag-  O  CN  -f  Nff4N03.       [556] 

Solution  of  urea  evaporated  with  argentic  nitrate. 


QffCl  =  ZfffOfC^  B  +  QNff4CL   [557] 

Compound  of  urea  and  hydrochloric  acid  heated  to  145°. 

3N2ff4  CO  =  3Nff*  +  Hf  O/  C3N-3.         [558] 

Urea  heated  alone  to  150°  -  170°. 

The  last  reaction  is  accompanied  by  another,  in  which  a  con- 
siderable portion  of  the  urea  is  converted  into  a  compound 
similar  to  itself  called  Biuret. 


2   2, 

Biuret. 

or  possibly  NHf  CO-NH-  CO-NH2. 

Biuret  ? 

484.  Compound  Ureas.  —  The  *atoms  of  hydrogen  in  urea 
may  be  replaced  by  various  hydrocarbon  positive  radicals. 
Thus  compounds  are  known  in  which  either  one,  two,  or  three 
of  the  four  hydrogen  atoms  in  the  urea  molecules  are  replaced 
by  ethyl  or  methyl,  but  the  substitution  of  the  fourth  hydrogen 
atom  by  these  radicals  has  not  been  effected.  Ethyl-urea,  di- 
ethyl-urea,  and  triethyl-urea  may  be  prepared  by  the  action  of 
ethylic  cyanate  on  ammonia,  ethylamine,  or  diethylamine  re- 
spectively1 (compare  also  [409]).  Of  these  bodies  diethyl-urea 
is  especially  noteworthy,  because  it  admits  of  two  isomeric 

1  Ethylic  cyanate  is  without  action  on  triethylamine,  and  an  analysis  of  the 
reactions  above  described  will  show  that  there  is  a  difference  of  condition  in 
this  case,  which  probably  explains  why  the  fourth  atom  of  hydrogen  in  urea 
cannot  be  replaced  by  this  method,  which  succeeds  so  well  for  the  first  three. 


§  485.]  MONUREIDES.  539 

modifications  (according  as  it  is  obtained  by  the  reaction  of 
ethylic  cyanate  on  ethylamine  or  of  potassic  cyanate  on  diethyl- 
ammonic  sulphate),  which  may  be  represented  thus :  — 
(ff,  C2ff5=N)-  CO(N=  CAff)  (H,H*N)-  CO(N=  C2ff6, O2ff&) 
The  first  of  these  when  treated  with  alkalies  yields  besides 
C02  simply  ethylamine,  the  second  a  mixture  of  diethylamine 
with  ammonia. 

By  means  of  the  dyad  radical  ethylene  we  can  bind  together 
two  molecules  of  urea  into  a  still  more  complex  group.  Thus, 
by  the  action  of  cyanic  acid  on  ethylene  diamine  (167),  we 
obtain 

H2N-CO-NH-  C,H,-HN-  CO-NH* 

Ethyelene-diurea. 

and  by  the  action  of  the  same  reagent  on  diethyl-ethylene-di- 
amine,  or  that  of  ethylic  cynate  on  ethylene-diamine,  we  ob- 
tain compounds  differing  from  the  last  only  in  that  two  of  the 
hydrogen  atoms  are  replaced  by  ethyl.  These  compounds 
furnish  another  example  of  isomerism,  similar  to  that  described 
above,  but  of  a  more  complex  type.  When  decomposed  by 
alkalies,  the  first  yields  besides  C02  a  mixture  of  diethyl-ethyl- 
ene-diamine  with  ammonia,  the  second  a  mixture  of  ethylene- 
diamine  with  ethylamine.  A  graphic  representation  of  these 
reactions  will  further  show  that  two  other  isomeric  modifica- 
tions of  the  same  compound  are  also  possible ;  the  one  giving, 
under  the  conditions  above  mentioned,  a  mixture  of  ethylene- 
diamine  with  diethylamine,  and  the  other  a  mixture  of  ethyl- 
ethylene-diamine,  ethylamine  and  ammonia. 

The  properties  and  reactions  of  these  compound  ureas  are 
analogous  to  those  of  urea  itself.  They  act  like  feeble  amine 
bases,  but  as  a  rule  they  unite  less  readily  with  acids  than 
normal  urea. 

485.  Monureides.  —  The  atoms  of  hydrogen  in  urea  may  be 
replaced  by  acid  as  well  as  by  positive  radicals,  and  there  thus 
results  a  most  remarkable  class  of  compounds,  which  have  all 
the  characters  of  true  amides.  Those  which  are  formed  after 
the  type  of  the  single  urea  molecule  are  called  monureides,  to 
distinguish  them  from  the  more  complex  though  similar  pro- 
ducts having  the  type  of  a  doubly  condensed  urea  molecule, 
the  diureides.  These  highly  complex  bodies,  like  the  simpler 
amides,  are  acid  when  the  replacing  radical  contains  one  or 


540  MONUKEIDES.  [§  485. 

more  atoms  of  oxatyl.  Otherwise,  they  are  neutral  or  feebly 
basic.  The  monureides  may  be  regarded  as  formed  by  the 
union  of  one  molecule  of  an  acid  with  one  molecule  of  urea, 
accompanied  by  the  elimination  of  one  or  two  molecules  of 
water,  a  reaction,  through  which  one  or  two  of  the  hydrogen 
atoms  in  the  urea  molecule  become  replaced  by  the  acid  radi- 
cal, thus  :  — 

CO)  00) 

HofGAO  +  ff2  }-N2  —  H20  =  ffo-C2H20  yN2 
JT*)  Bt) 

Glycollic  Acid.  Urea.  Glycoluric  Acid. 

CO)  00) 

=  02ff20  }-Nz 


Glycolyl  Urea  (Hydantoin). 

In  like  manner  we  may  derive,  at  least  theoretically,  the  sev- 
eral monureides  included  in  the  second  and  third  columns  of 
the  following  table  from  the  corresponding  acids  included  in 
the  first  column.  Monobasic  acids  can  of  course  yield  only 
one  derivative,  and  that  must  be  neutral.  Dibasic  acids,  on  the 
other  hand,  yield  two,  one  acid  and  one  neutral. 

Acids.  Monureides.  Monureides. 


CO 
ffofCO  Ho-  CO 


O  ) 
O  5- 

TJ   V 


Carbonic  Acid. 

Allophanic  Acid. 

CO  CO 


Oxalic  Acid.  j 

Oxaluric  Acid.  ParaTban . 

CO  )  CO 

Hof  C3  Os  Ho-  C3  Os  >  N2  C8  Oo 

Mesoxalic  Acid.  TT  (  TT 

***)  n% 

Alloxanic  Acid.  Alloxan. 

CO  ) 

Ho-C2ff,0  C2H,0[N2 

Acetic  Acid.  jj  \ 

Acetyl  Urea. 

CO  )  CO 


Glycollic  Acid.          •  TT 

-o3  )  J 

Glycoluric  Acid.  Hydantoin. 


486.] 
Acids. 


ffo2=C3ff202 

Malonic  Acid. 


DIUREIDES. 
Monureides. 


541 


Monureides. 
CO 


Barbituric  Acid. 

CO) 


Tartronic  Acid. 


H-(CO-CO)-Ho 

Glyoxalic  Acid. 


Dialuric  Acid. 


CO 
ff-(CO-CO) 


Allanturic  Acid. 


486.  Diureides.  —  These  may  be  regarded  as  formed  by  the 
union  of  a  monureide  with  an  additional  molecule  of  urea, 
the  combination  involving  as  before  the  elimination  of  one  or 
two  molecules  of  water.  The  following  are  a  few  examples  :  — 


CO  ) 
ffo-C2H20  V- 


CO 


Glycoluric  Acid. 


CO 
H-C202 


N 


CO  ) 


C 

CO 
—  H20  =  H-C202 


AUanturic  Acid. 


CO 

ffo-C3H02 
H, 

Dialuric  Acid 


Urea. 


Allan  toin. 


CO  J 

ff2) 

Urea. 


Barbituric  Acid. 


Xan  thine. 


°") 

o(N 

Caff,0  p 

ffj 

Hypoxanthine. 


542  URIC  ACID.  [§487. 

It  must  not  be  inferred  that  the  equations  either  of  this  or  of 
the  last  section  represent  actual  processes  by  which  the  various 
urides  have  been  prepared.  They  merely  indicate  the  most 
probable  theory  in  regard  to  the  constitution  and  chemical  re- 
lations of  these  bodies  which  we  have  been  able  to  form.  The 
substances  themselves  are  either  products  of  the  animal  organism, 
or  else  have  been  prepared  from  such  products  by  different  chem- 
ical processes,  and  our  only  knowledge  in  regard  to  their  mo- 
lecular structure  has  been  derived  from  a  study  of  their  prop- 
erties, and  of  the  chemical  changes  in  which  they  are  formed 
or  broken  up.  For  the  evidence  on  which  the  rational  sym- 
bols here  given  are  based  we  refer  the  student  to  the  memoirs 
of  Baeyer,  in  the  Annalen  der  Chemie  und  Pharmacie,  contain- 
ing the  results  of  his  very  extended  investigations  of  this  class 
of  compounds.1 

487.  Uric  Acid  is  not  only  the  most  important  of  the  ureides, 
but  it  is  the  source  from  which  almost  all  the  rest  have  been 
derived.  It  is  a  constant  product  of  the  animal  organism,  re- 
sulting from  the  imperfect  oxidation  of  the  nitrogenized  tissues. 
With  the  reptiles,  birds,  and  insects  it  forms  (in  combination 
with  ammonia)  the  chief  part,  and  in  some  cases  nearly  the 
whole,  of  their  solid  excrements  ;  but  in  mammalia  the  oxidation 
proceeds  further  in  the  body  and  the  product  voided  is  princi- 
pally urea.  Nevertheless,  uric  acid  is  always  present  in  human 
urine,  and  in  certain  abnormal  states  of  the  system  the  amount 
becomes  increased  to  an  injurious  extent,  giving  rise  to  sedi- 
ment, gravel,  or  calculi.  In  some  forms  of  gout  all  the  fluids 
of  the  body  become  saturated  with  it,  and  in  combination  with 
soda  it  is  deposited  in  the  joints,  forming  what  are  familiarly 
known  as  chalk  stones. 

Uric  acid,  when  pure,  forms  a  white  crystalline  powder, 
which  under  the  microscope  exhibits  definite  and  character- 
istic crystalline  forms  ;  but  the  crude  acid  is  more  or  less  tinted 
by  the  coloring  matter  of  the  urinary  secretion,  from  which  it 
is  prepared.  When  heated,  it  decomposes  without  melting, 
yielding  a  sublimate  of  cyanuric  acid,  ammonic  cyanate  (or 
urea),  and  ammonic  carbonate,  leaving  a  carbonaceous  residue 

1  See,  also,  an  article  in  Silliman's  Journal,  vol.  96,  page  289,  by  Dr.  W. 
Gibbs,  in  which  rational  symbols  for  these  bodies  are  theoretically  deduced 
from  either  the  known  or  assumed  polymeric  forms  of  cyanic  acid. 


§  487.]  URIC  ACID.  543 

behind.  It  is  almost  insoluble  in  water  and  the  dilute  mineral 
acids;  but  it  dissolves  readily  in  alkaline  solutions,  since  it 
forms  with  the  alkaline  radicals  more  or  less  soluble  salts.  It 
also  forms  salts  with  several  of  the  more  basic  metallic  rad- 
icals, which  may  either  replace  one  or  two  of  its  typical  hydro- 
gen atoms.  We  have,  therefore,  in  several  cases  both  an  acid 
and  a  basic  salt  of  the  same  radical.  But  while  we  can  only 
replace  two  of  the  hydrogen  atoms  with  metallic  radicals  we 
can  replace  three  with  ethyl. 

The  rational  formula  of  uric  acid  has  alre^iy  been  given. 
It  is  based  chiefly  on  the  following  considerations.  When  the 
acid  is  treated  with  a  mixture  of  hydrochloric  acid  and  potas- 
sic  chlorate  (a  strong  oxidizing  acid),  it  is  converted  wholly 
into  a  mixture  of  alloxan  and  urea, 

N&  C503+0  +  H20  =  N2ff2  C4  0,  +  N2H,  CO.     [559] 

Uric  Acid.  Alloxan.  Urea. 

Now  the  first  effect  of  the  oxidation  would  be  naturally  to  re- 
move the  hydrogen  atoms  from  the  hydrocarbon  radical  we 
have  assumed  to  exist  in  uric  acid,  changing  it  into  the  hypo- 
thetical compound  N4ff2C503,  and  then  this,  by  absorbing  two 
molecules  of  water,  gives  at  once  alloxan  and  urea. 

CO)          CO) 

jV2-f-//2>^V2.  [560] 

•"2 '  ""a'  ""a  t  v  J 

Uric  Acid.          Hypothetical  Intermediate.  Alloxan.  Urea. 

Further,  when  alloxan  is  boiled  with  an  alkaline  solution  it 
yields  urea  and  the  mesoxalate  of  the  alkaline  radical.  Lastly, 
mesoxalic  acid  is  a  crystalline  solid  resembling  oxalic  acid,  and 
like  it  is  dibasic.  As  its  composition  is  well  determined  there 
can  be  no  question  that  it  contains  the  radical  C3  03,  and  is  the 
third  term  of  a  series  of  which  carbonic  acid  and  oxalic  acid 
are  the  other  three. 

AlOcT  \J  \J  JLlOf  C/2  C/2  -tlOf  ^3  ^/3* 

Carbonic  Acid.  Oxalic  Acid.  Mesoxalic  Acid. 

This  completes  the  chain  of  evidence,  but  the  student  will  not 
fail  to  see  that  it  has  a  weak  point. 

The  view  of  the  constitution  of  uric  acid  here  adopted  is 
further  supported  by  a  reaction  observed  by  Strecker,  who 
found  that,  when  treated  with  hydriodic  acid,  one  molecule  of 
uric  acid  breaks  up  into  one  molecule  of  glycocoll  (L 


544 


UEIC  ACID. 


[§  487. 


,  three  molecules  of  ammonia  and  three  of  carbonic  di- 
oxide. Now  if  uric  acid  contains,  as  we  have  assumed,  the 
tartronyl  radical,  it  must  have  the  graphic  symbol  given  below, 
leaving  the  parts  in  brackets  undeveloped  (473),  and  by  com- 
paring this  with  the  symbols  of  tartronic  acid  and  glycocoll  on 
either  side,  it  can  readily  be  seen  that  the  products  are  pre- 
cisely such  as  might  be  expected  from  the  action  of  the  reagent 
used,  assuming  of  course  that  our  theory  is  correct. 

OHO  OH,0  OH 

Ho-G-C-C-Ho          (NBfrQ-G&(Ni<$          (NH2)-C-C-H. 
Ho  Ho  Ho 

Tartronic  Acid.  Uric  Acid.  GlycocolL 

Uric  acid  is  remarkable  for  the  facility  with  which  it  is  al- 
tered by  oxidizing  agents,  and  for  the  great  number  of  definite 
and  crystallizable  compounds  obtained,  either  in  this  manner  or 
by  treating  the  immediate  products  of  oxidation  with  various 
reagents.  The  following  list  includes  all  the  more  important 
derivations :  — 


Derivatives 


Br 


of  Uric  Acid, 
Hydantoin, 
Hydurilic  Acid, 
Leucoturic  Acid, 
Mesoxalic  Acid, 
Murexide, 
Mycomelic  Acid, 
Oxaluric  Acid, 
Paraban, 

Pseudo-uric  Acid, 
Srryphnic  Acid, 
Thionuric  Acid, 
Uramil, 
Urinilic  Acid, 
Uroxanic  Acid, 
Violantin, 
Violuric  Acid, 
Xanthine, 


Allantoin, 
Allanturic  Acid, 
Allituric  Acid, 
Alloxan, 
Alloxanic  Acid, 
Alloxantin, 
Barbituric  Acid, 
Bromo-barbituric  > 

Acid,  > 

Dibromo-barbituric  ) 

Acid,  J 

Dibarbituric  Acid, 
Dialuric  Acid, 
Dilituric  Acid, 
Glycoluric  Acid, 
Glycoluril, 
Hydantoic  Acid, 


It  must  not  be  supposed  that  the  term  acid,  used  in  connection 
with  so  many  of  these  compounds,  implies  that  they  all  have 
the  constitution  of  true  organic  acids,  that  is,  contain  one  or 
more  atoms  of  oxatyl.  That  there  are  among  them  true  acid 


§487.]  UBIC  ACID.  545 

amides  (168)  has  already  been  shown,  but  in  most  cases  the 
apparent  acid  reaction  arises  from  the  power,  which  many 
amides  possess,  of  exchanging  one  or  more  of  their  atoms  of 
typical  hydrogen  for  the  basic  radicals  of  metallic  hydrates, 
and  this  relation  undoubtedly  shows  that  the  molecules  of  these 
bodies  are  in  a  polar  condition  not  unlike,  although  less  marked, 
than  that  of  the  true  acid  molecules  of  the  water  type. 

For  the  various  processes  by  which  the  uric  acid  derivatives 
have  been  prepared  we  must  refer  the  student  to  Watt's  Dic- 
tionary of  Chemistry,  from  which,  with  some  alterations,  the 
above  table  has  been  taken.  But  in  spite  of  the  apparent  com- 
plexity of  the  results,  the  chemical  changes  involved  in  the 
production  of  these  bodies  may  be  referred  to  a  few  types. 
We  may  have  :  — 

First.  The  breaking  up  of  a  diureide  into  a  monureide  and 
urea. 

co\  ao)       °°) 

C,Hf>  }  N<  +  H*°  =  °^°  t  N*  +^2  f  N*     t561] 

77  1  fii}  ^2  ) 

•**4   '  Hydantoin.  Urea. 

Glycoluril. 

By  boiling  a  solution  of  glycoluril  with  acids,  and  the  reaction  [560]  given, 
above  is  an  example  of  a  similar  change. 

Secondly.   The  formation  of  a  biureide  from  a  ureide. 

2tf2K20404  —  0  =  N4ff40807.  [562] 

Alloxan.  Alloxantin. 

By  the  action  ofhydric  sulphide  or  nascent  hydrogen  on  a  solution  of  alloxan. 
Thirdly.    A  modification  of  the  more  complex  radical  of  the 
ureide,  without  altering  its  relations  to  the  compound. 

CO)  CO  ) 

C80»  \-&2  +  0  =  C202  V-  N2  +  00,        [563] 
#2)  H,\ 

Alloxan.  Paraban. 

By  gently  warming  alloxan  with  nitric  acid. 

.O&  +  0  +  ff20  =  N4ff6040s  +  002. 

Uric  Acid.  Allantoin. 

By  boiling  uric  acid  with  water  and  plumbic  dioxide., 


4   3          2         ,,  04  0*+H,  0.  [564] 

Allantoin.  Glycoluril.  ~ 

By  the  action  of  sodium  amalgam  on  a  solution  of  allantoin. 

CO)  00) 

C2H2BrO  y#a=±  HBr  +  O2ff20  f-  N2          [565] 
«)  ff9) 

Bromacetyl  Urea.  Hydantoin, 

By  the  action  of  ammonia. 


546  ALLANTOIN  AND  MUREXIDE.  [§488. 

CO)  CO) 

=  CSH(NO,)  0,  [  N2  [566] 


Barbituric  Acid.  Nitrobarbituric  or 

Dilituric  Acid. 

By  the  action  of  nitric  acid. 

CO)  CO) 

C303  kJ5  +  ff20  =  ffo-C303  [.JK  [567] 

HI)  ff3) 

Alioxan.  Alloxanic  Acid. 

Fourthly.  A  breaking  up  of  the  ureide  into  ammonia  and 
the  hydrate  of  its  principal  radical. 

CO) 

C303^N-2  +  3ff20=C02  +  IfofC303  +  2NIf3    [568] 

IT  \  Mesoxalic  Acid. 

^2  ) 

Alioxan. 

CO) 
C3ff202  [N'2  +  3ff20  =  C02  +  ffo2=C3ff20,  +  2NIT3  [569] 

77"  V  MalonicAcid. 

^2  ) 

Barbituric  Acid. 

By  heating  with  solutions  of  caustic  alkalies. 

It  will,  of  course,  be  understood  that  in  the  actual  processes 
two  or  more  of  such  reactions  as  have  been  here  illustrated 
may  concur  or  may  succeed  each  other.  Indeed,  it  has  been 
found  very  difficult  to  isolate  them. 

488.  Allantoin  and  Murexide  are  the  only  bodies  among 
the  uric  acid  derivatives  which  have  any  other  interest  than 
that  which  is  connected  with  their  chemical  composition,  and 
the  only  special  interest  attaching  to  allantoin  arises  from 
the  isolated  fact  that  it  appears  to  be  an  essential  constituent 
of  the  allantoic  liquid.  Murexide,  however,  is  a  most  brilliant 
purple  pigment,  and  before  it  was  superseded  by  the  aniline 
colors  was  manufactured  on  a  large  scale.  It  can  be  readily 
prepared  by  adding  ammonia  to  the  solution  of  alloxan  and 
alloxantin,  which  is  obtained  by  dissolving  uric  acid  in  dilute 
nitric  acid  under  regulated  conditions,  and  the  production  of  a 
purple  color  under  such  circumstances  is  a  delicate  test  for  uric 
acid.  Murexide  crystallizes  in  brilliant  garnet-colored  prisms, 
which  appear  gold-green  by  reflected  light.  It  gives  with  wa- 
ter a  rich  purple  solution,  but  is  insoluble  in  alcohol  or  ether. 
It  appears  to  be  the  ammonium  salt  of  a  very  complex  amide, 
which  has  been  called  purpuric  acid  ;  but  although  the  ammo- 
nium radical  may  be  readily  replaced  by  various  metals  the 


§489.]  GUANINE  AND  GUANIDINE.  547 

amide  itself  has  not  been  isolated,  and  our  knowledge  in  regard 
to  these  beautiful  compounds  is  as  yet  too  limited  to  enable  us 
to  assign  to  them  any  probable  rational  symbols.  Similar  pro- 
ducts are  obtained  by  the  action  of  potassic  cyanides  on  picric 
acid  (457),  and  these  isopurpurates,  as  they  are  called,  are 
isomeric  with  the  corresponding  uric  acid  derivatives. 

489.  Gkianine  and  Guanidine.  —  The  first  of  these  com- 
pounds resembles  uric  acid,  and  is  found  associated  with  it  in 
some  kinds  of  guano,  but  it  forms  an  amorphous  instead  of  a 
crystalline  powder,  and  has  basic  rather  than  acid  relations. 
Ultimate  analysis  gives  the  empirical  symbol  Jf5N5O50,  and  it 
may  be  regarded  as  derived  from  xanthine  by  replacing  the 
radical  HO  by  H2N,  —  a  view  of  its  constitution  which  is  sus- 
tained by  the  fact  that  when  treated  with  nitrous  acid  it  yields 
that  well-known  diureide, 


[570] 

Guanine.  Xanthine. 

An  equally  interesting  reaction  is  obtained  by  digesting  guanine 
with  a  mixture  of  hydrochloric  acid  and  potassic  chlorate,  when 
it  breaks  up  into  paraban  and  a  remarkable  amine  called 
guanidine. 


Guanme'  H5N,  0  +  H2N,  03  03  +  002.      [571] 

Guanidine.  Faraban. 

There  are  also  formed  at  the  same  time,  although  in  smaller 
quantities,  xanthine,  oxaluric  acid,  and  urea. 

Guanidine  is  a  crystalline  solid  having  a  strong  basic  reac- 
tion, absorbing  C02  from  the  air,  and  forming  with  acids  crys- 
talline salts,  which,  like  H5N3  O  .  ffCl,  contain  for  every  mole- 
cule of  a  monobasic  acid  one  molecule  of  the  amine.  It  can 
be  formed  synthetically  by  heating  iodide  of  cyanogen  with  an 
alcoholic  solution  of  ammonia  in  a  closed  tube,  and  this  reac- 
tion leaves  no  doubt  in  regard  to  its  molecular  structure. 


HI.         [572] 

Guanidine  has  also  been  obtained  by  heating  with  the  same 
solution,  and  under  similar  conditions,  chlorpicrin,  a  product  of 
the  action  of  chlorine  on  picric  acid. 


Chlorpicru,  ff^  Q  .  ffCl  +  2ffCl  +  HN03.       [573] 


548       GLYCOCYAMIN  AND  GLYCOCYAMIDINE.    [§  490. 

The  interpretation  of  this  reaction  is  aided  by  the  fact  that 
when  the  same  chlorpicrin  is  distilled  with  alcohol  and  sodium 
it  yields  an  ether  which  is  a  true  ortho-carbonate,  thus  :  — 


(  G2ff5)/  Of  G  +  3Na  Gl  +  NaN02.     [574] 

The  same  ether,  heated  with  aqua  ammonia  in  a  closed  tube, 
gives  guanidine. 

jgfc4i  04i  G  +  3  Nff3  =  ±Et-  OH  +  HN=  G-(NHZ\.  [575] 
There  are  also  known  a  number  of  well-marked  amine  bases, 
which  may  be  regarded  as  derived  from  guanidine  by  replacing 
one,  two,  or  three  atoms  of  its  typical  hydrogen  by  hydrocar- 
bon radicals. 

490.  Glycocyamin  and  Glycocyamidine,  Greatine  and  Grea- 
tinine.  —  By  passing  chloride  of  cyanogen  and  ammonia  gas 
simultaneously  into  anhydrous  ether,  the  ammonic  chloride 
which  is  formed  separates  out,  while  there  remains  in  solution 
one  of  the  simplest  and  at  the  same  time  most  remarkable 
compounds  of  the  amide  group. 


CN-Ol  +  2Nffs  —  NfffCN  +  NHAGl.        [576J 

Cyanamide. 

Now  we  can  directly  unite  the  cyanamide  thus  formed  with 
glycocoll,  and  the  product  is  called  glycocyamine,  which  when 
acted  upon  by  dry  HGl  yields  an  allied  base  called  glycocyami- 
dine.  The  constitution  of  these  bodies  can  be  inferred  with 
great  certainty  from  the  simple  synthetical  process  by  which 
the  first  is  formed,  interpreted  by  reactions  [572]  and  [576]. 
It  will  be  noticed  that  the  factors  in  these  two  reactions  are 
nearly  the  same,  and  the  difference  in  the  products  depends  on 
slight  variations  of  conditions.  Indeed,  guanidine  may  be  ob- 
tained by  the  action  of  NH8  on  the  chloride  as  well  as  on  the 
iodide  of  cyanogen,  only  it  is  not  then  the  chief  product,  for 
the  reaction  tends  to  take  the  form  of  [576]  rather  than  of 
[572].  An  analysis  of  these  reactions  will  show  that  the  dif- 
ference in  the  results  depends  on  the  circumstance  that,  while 
in  [576]  the  two  atoms  in  the  cyanogen  radical  remain  united 
by  the  three  original  bonds,  in  [572]  one  of  these  bonds  is  let 
Joose,  forming  points  of  attachment  to  which  the  two  radicals 
jfiTand  NH2  join  themselves.  Now  the  union  of  glycocoll  with 
cyanamide  probably  depends  on  a  similar  change,  so  that  in 


§490.]  CREATINE  AND  CREATININE.  549 

the  resulting  glycocyamine  the  two  atoms  in  the  original  cya- 
nogen radical  remain  joined  by  two  bonds,  while  the  two  parts 
of  the  glycocoll  molecule,  NH2  and  HO~O2H20,  unite  to  the 
points  of  attachment  which  the  breaking  of  the  third  bond  fur- 
nishes. The  subsequent  production  of  glycocyamide  is  simply 
an  example  of  the  change  from  a  monad  to  a  dyad  radical  by 
the  elimination  of  HO  with  which  we  are  so  familiar  (485). 

The  interest  attaching  to  the  above  compounds  arises  from 
the  fact  that  there  is  found  in  muscular  juice  a  crystalline  base 
called  creatine  (supposed  to  have  important  physiological  rela- 
tions), which  is  the  first  homologue  of  glycocyamine,  and  which 
yields,  when  treated  with  acids,  a  second  base,  creatinine,  that 
is  the  first  homologue  of  glycocyamide.  Thus  we  have  the 
following  triamides:  — 

C  )  O  } 

jr}*!         Ho-02H2olN,  C2H20  IN, 

Guanidine.  Glycocyamine.  Glycocyamidine. 

C  \  C 

Ho-C2H20  (N  C2H20  ,N 

OH,  pVs  OH3  ^ 


Creatine.  Creatinine. 

Both  creatine  and  creatinine  have  been  found  not  only  in  mus- 
cular flesh,  but  also  in  the  urine,  in  the  blood,  and  in  other  ani- 
mal fluids ;  but  it  is  difficult  to  determine  to  what  relative 
extent  they  exist  in  the  living  body,  since,  while  strong  acids 
convert  creatine  into  creatinine,  alkaline  reagents  change  crea- 
tine back  to  creatinine,  and  these  changes  may  take  place  in 
the  processes  of  extraction.  These  bases  unite  directly  with 
acids,  forming  well-crystallized  salts,  and  one  molecule  of  base 
neutralizes  in  each  case  one  molecule  of  a  monobasic  acid. 

Creatine  has  been  formed  synthetically  by  a  process  which 
plainly  indicates  its  molecular  constitution  ;  for  as  glycocya- 
mine results  from  the  union  of  cyanarnide  with  glycocoll,  so 
creatine  is  the  product  of  the  union  of  cyanamide  with  methyl- 
glycocoll,  a  compound  usually  called  sarcosine,  and  the  reac- 
tions below,  which  show  that  sarcosine  is  really  methyl-glyco- 
coll,  complete  the  evidence. 

1st.  Synthesis  of  glycocoll. 
Ho-(  ry720)- C1  +  &ff3  =  Ho-(  C,ff2 0)-N=ff2  +  HCl.    [577] 

Chloracetic  Acid.  Glycocoll.  L          J 


550  CAFFEINE  AND  THEOBROMINE.  [§492. 

2d.  Synthesis  of  sarcosine. 
Ho-(C2ff20)~Cl  +  J»i(  CH9)&  = 

Methylamine. 

Ho-(  GA  0)-N-(  GH,\H  -f  HOI.     [578] 


491.  Caffeine  and  Theobromine.  —  These  well-known  or- 
ganic bases  which  are  regarded  as  the  active  agents  in  tea  and 
coffee  on  the  one  hand,  and  in  the  cacao-bean  on  the  other,  are 
closely  allied  to  the  class  of  compounds  we  have  been  studying. 
They  are  probably  the  methyl  substitution  products  of  a  sim- 
pler amide  not  yet  discovered.  That  caffeine  is  methyl-theo- 
bromine  there  is  no  doubt,  for  theobromine  can  be  converted 
into  caffeine  by  a  simple  process  of  substitution.  It  is  also 
probable  that  theobromine  itself  contains  methyl,  for  when 
caffeine  is  oxidized  by  chlorine  and  water  it  yields  well-known 
dimethyl  products.  Moreover,  these  products  are  the  methyl- 
ated forms  of  two  well-known  uric  acid  derivatives,  viz.  allo- 
xanthine  and  paraban,  indicating  that  caffeine  and  theobromine 
are  allied  to  the  diureides.  Now  it  appears  from  their  empiri- 
cal symbols  that  theobromine  differs  from  xanthine  by  just 
(<7#2)2,  thus:  — 


Xanthine.  Theobromine.  Caffeine. 

But  theobromine  can  not  be  simply  dimethyl-xanthine,  for  this 
last  compound  has  been  made,  and  although  isomeric  with  theo- 
bromine is  not  the  same  substance.  When  caffeine  is  treated 
with  baric  hydrate  there  is  formed  during  the  first  stage  of 
the  process  a  new  base  called  caffeidine,  but  this  is  subsequently 
decomposed,  and  the  ultimate  products  of  the  reaction  are,  be- 
sides carbonic  dioxide  and  ammonia,  formic  acid,  methylamine, 
and  sarcosine.  Creatine  similarly  treated  yields,  besides  car- 
bonic dioxide  and  ammonia,  only  sarcosine,  and  these  reactions 
indicate  that  the  unknown  amide,  of  which  caffeine  is  a  methyl- 
ated substitution  product,  is  allied  to  creatine,  probably  con- 
taining like  this  the  glycol  radical. 

492.  Vegetable  Alkaloids.  —  The  active  principles  of  many 
medicinal  or  poisonous  plants  are  cry  stall  izable  bodies,  which 
closely  resemble  in  their  general  properties  and  chemical  re- 
lations the  complex  amines  or  basic  amides  we  have  been  study- 
ing. Several  of  them,  like  quinine  and  morphine,  are  well- 
known  articles  of  the  materia  medica,  and  are  perhaps  the 


§  492.]  VEGETABLE  ALKALOIDS.  551 

most  valuable  medicinal  agents  which  we  possess.  As  a  gen- 
eral rule  they  are  soluble  in  water,  have  a  strong,  bitter  taste, 
and  form  well-marked  crystalline  salts  with  acids.  Hence  the 
name  of  vegetable  alkaloids.  The  number  of  these  bodies 
now  known  is  exceedingly  large.  The  dried  juice  of  the 
poppy,  which  we  call  opium,  alone  contains  not  less  than  eight 
distinct  bases.  Two  of  the  alkaloids,  conine  and  nicotine, 
from  the  hemlock  and  tobacco  plant  respectively,  are  volatile 
oily  liquids,  and  they  do  not  contain  oxygen.  The  great  body, 
however,  of  the  alkaloids  are  oxygenated  compounds,  and  can- 
not be  distilled  without  decomposition.  These  two  classes  of 
alkaloids  correspond  to  the  volatile  amines  on  the  one  hand, 
and  the  non-volatile  ammonium  bases  on  the  other ;  but  no  safe 
conclusion  in  regard  to  their  constitution  can  be  drawn  from 
this  seeming  analogy,  for  not  only  are  the  facts  we  have  been 
studying  sufficient  to  show  that  the  class  of  amines  or  alkaline 
amides  includes  many  non-volatile  oxygenated  bases,  but  all 
the  natural  alkaloids  combine  directly  with  acids  in  forming 
salts.  Moreover,  in  several  cases  we  are  able  to  substitute 
hydrocarbon  radicals  for  one  or  more  of  the  hydrogen  atoms  of 
the  alkaloid,  and  obtain  bodies  which,  like  the  ammonium  bases, 
eliminate  water  when  they  combine  with  acids. 

Among  the  most  important  of  the  vegetable  alkaloids  may 
be  mentioned  morphine,  narcotine,  and  codeine  from  opium; 
quinine  and  cinchonine  from  cinchona  bark ;  strychnine  and 
brucine  from  nux-vomica  and  other  strychnos  plants ;  aconi- 
tine  from  the  monkshood ;  atropine  from  belladonna  and  stra- 
monium ;  veratrine  from  the  white  hellebore.  All  these  sub- 
stances have  been  carefully  studied,  and  their  general  properties 
and  chemical  relations  are  accurately  known.  Their  empirical 
formulae  show  that  with  few  exceptions  they  must  be  very 
complex  bodies,  but  beyond  this  very  little  has  been  made  out 
in  regard  to  their  chemical  constitution.  In  several  cases  the 
number  of  replaceable  atoms  of  hydrogen  have  been  deter- 
mined, and  in  others  the  natural  alkaloid  has  been  proved  to 
be  a  methylated  substitution  product  of  a  simpler  base,  but  in 
no  case  has  the  molecular  structure  been  fully  developed.  The 
great  difficulty  encountered  in  investigating  the  constitution  of 
these  bodies  arises  from  the  fact  that  we  know  of  no  reagent 
by  which  we  can  replace  nitrogen  by  monad  radicals,  and  thus 


552  AMINE-AMIDES,   OR   ALKAMIDES.  [§493. 

break  up  the  alkaloid  into  the  several  atomic  groups  of  which 
it  consists,  without  decomposing  the  radicals  also.  The  student 
should  study  in  this  connection  the  important  investigation  of 
Matthiessen  l  on  morphine  and  codeine,  and  that  of  Schiff2  on 
conine,  the  first  alkaloid  which  has  been  produced  synthetically. 
493.  Amine-Amides,  or  Alkamides.  —  It  must  have  been 
noticed  that  with  the  complex  compounds  we  have  been  re- 
cently studying,  the  clear  distinction  between  amines  and 
amides  previously  drawn  (167,  168)  is  almost  wholly  obscured. 
The  effect  of  introducing  several  radicals,  both  acid  and  basic, 
into  the  same  ammonia  group,  cannot  be  traced  to  any  general 
principle.  The  resulting  molecule  has  sometimes  basic  and 
sometimes  acid  relations.  Hence  it  is  that  we  have  been 
obliged  to  class  with  the  amides  so  many  substances  having 
well-marked  alkaline  properties,  and  for  this  reason  many 
chemists  distinguish  a  third  class  of  compounds  under  the  am- 
monia type,  to  which  they  give  the  name  of  arnine-amides  or 
alkamides  (alkaline  amides).  An  alkamide  is  frequently  de- 
fined as  a  compound  of  the  ammonia  type,  in  which  the  hydro- 
gen atoms  are  in  part  replaced  by  basic  and  in  part  by  acid 
radicals;  but  we  prefer  to  give  to  the  term  the  simple  meaning 
which  the  derivation  indicates,  for  urea,  which  contains  only  an 
acid  radical,  is  one  of  the  best-defined  bodies  of  the  cla^s,  at 
least  if  we  accept  the  view  of  its  constitution  usually  taken. 
The  distinction  has  not  been  before  made  in  this  book,  because 
the  study  of  the  alkamides  cannot  well  be  separated  from  that 
of  the  true  amides  to  which  they  are  so  closely  related ;  and 
since  several  of  the  more  important  of  these  compounds  have 
already  been  described,  further  examples  are  unnecessary. 

1  Proceedings  of  the  Royal  Society  of  London,  XVII.  455  ;   also,  Ann. 
Chem.  und  Pharm.,  VII.  Supplementband,  170. 
a  Berichte  der  Deutschen  chem.,  Gesellschaft,  Jahrgang,  HI.  946. 


§494.]  ALCOHOLS  AND   THEIR  DERIVATIVES.  553 


Alcohols  and  their  Derivatives. 

494.  Chlorals.  —  The  white  solid  which  is  the  ultimate  re- 
sult of  the  action  of  chlorine  gas  on  absolute  alcohol  is  a  com- 
pound of  alcohol  with  one  of  its  chlorinated  derivates  called 
chloral.  When  the  crude  product  of  this  reaction  is  treated 
with  strong  sulphuric  acid  the  chloral  separates  out,  and  may 
be  decanted  and  purified  by  repeated  distillation  over  lime.  It 
is  a  thin  colorless  oil,  having  a  pungent  odor  and  astringent 
taste,  boiling  at  98°6,  with  Sp.  Gr.  —  1.49  and  Sp.  Gr.  = 
74.04.  It  readily  dissolves  in  water,  yielding  a  neutral  solution 
which  does  riot  precipitate  nitrate  of  silver,  but  in  so  dissolving 
it  enters  into  combination,  and  if  the  amount  of  water  is  small 
the  union  is  attended  with  a  marked  elevation  of  temperature. 
If  the  amount  taken  is  about  one  eighth  of  the  weight  of  the 
chloral  the  whole  mass  solidifies,  and  the  white  translucent  solid 
thus  formed  is  the  familiar  preparation  which  is  now  so  highly 
valued  as  an  anesthetic  agent.  Chloral  Hydrate  has  a  strong, 
pungent,  ethereal  odor,  volatilizes  gradually  in  the  air,  and  dis- 
tils without  decomposition  when  heated.  It  melts  at  50°  to  51°, 
boils  at  97°  to  99°,  has  Sp.  Gr.  =  1.61  and  Sp.  Gr.  =  39.84, 
showing  that  chloral  and  water  are  disassociated  at  100°.  This 
substance  was  discovered  by  Liebig  in  1832,  but  it  is  only  re- 
cently that  its  valuable  medicinal  qualities  have  been  appreci- 
ated or  its  chemical  relations  fully  understood. 

Chloral  is  a  chlor-aldehyde,  and  has  the  same  structure  as 
acetic  aldehyde,  but  contains  Cl$  in  place  of  the  fl3  in  the 
methyl  radical. 

CfffCO-ff  CClfCOIL 

Acetic  Aldehyde.  Acetic  Chloral. 

Its  constitution  is  shown  by  the  following  reactions  :  1st. 
Acetic  aldehyde  when  acted  on  by  chlorine  gas,  under  regu- 
lated conditions,  is  converted  into  chloral.  2d.  Chloral  when 
acted  on  by  nascent  hydrogen  chapges  back  to  aldehyde.  3d. 
Chloral  combines  with  NH&  forming  a  compound  correspond- 
ing to  aldehyde  ammonia.  4th.  Oxidizing  agents  convert  chlo- 
ral into  chloracetic  acid  (31)  and  [479]. 

When  chloral  or  its  hydrate  is  treated  with  a  solution  of 
a  caustic  alkali  it  yields  chloroform,  together  with  a  formiate 
24 


554  CHLORALS.  [§  494. 

of  the  alkaline  metal,  and  the  value  of  the  hydrate  as  an 
anesthetic  agent  seems  to  depend  on  the  fact  that  a  similar  re- 
action takes  place  in  the  blood. 

(OOls)-OOH+(K-OyH=K-0-(00-ff)  +  CClfff.  [579] 

Chloral.  Potassic  Formate.  Chloroform. 

When  chloral  is  heated  with  nitric  acid  there  is  formed,  be- 
sides chloracetic  acid,  which  is  the  direct  product  of  the  oxida- 
tion due  to  this  reagent,  also  a  small  amount  of  a  substance 
called  chlorpicrin.  The  last  is  the  product  of  a  metathesis  be- 
tween the  radicals  of  the  acid  and  the  chloral,  thus  :  — 

(OO13)-00-H  +  (ff-O)-NO,  = 

choral.  H-(>(CO:H)  +  CCls(N02).    [580] 

Formic  Acid.  Chlorpicrin. 

It  will  be  noticed  that  while  in  this  reaction  the  radical  OO13 
changes  place  with  HO,  in  the  previous  reaction  it  changed 
place  with  KO,  and  this  fact  is  a  most  striking  illustration  of 
the  theory  of  chemical  polarity.  Chlorpicrin  is  an  oily  liquid, 
usually  obtained  by  the  action  of  chlorine  on  picric  acid,  and 
may  be  regardad  as  chloroform  in  which  the  remaining  hydro- 
gen atom  has  been  replaced  by  N02. 

Chloral  combines  not  only  with  water  and  with  ethylic  al- 
cohol, but  also  with  other  alcohols  of  the  same  family,  with 
urea,  and  with  several  amides.  These  products  are  generally 
regarded  as  molecular  compounds,  but  it  is  more  probable  that 
they  have  the  constitution  represented  in  the  scheme  below  :  — 

(  OH3-  Off)-  0  (  O  Clf  Off)-  0. 

Acetic  Aldehyde.  Chloral. 


Chloral  Hydrate. 

(OOl3-OH)-Eto,Ho. 

Chloral  Hydro-ethylate. 

(  Cff3-  Off)-Mo2  (  COlf  OH  )=Eto2. 

Acetal.  Chloral  Diethylate. 

As  here  represented,  the  Compounds,  with  water  and  alcohol, 
are  intermediate  terms  between  chloral  and  another  substitution 
product,  which  bears  the  same  relation  to  acetal  l  that  chloral 

1  Acetal  is  a  well-known  product  of  the  oxidation  of  ethvlic  alcohol.  It 
contains  the  radical  ethylidene,  and  differs  both  in  Sp.  Gr.  and  boiling-point 
from  an  isomeric  compound  containing  ethylene,  which  has  also  been  isolated. 


§  495.]  MELLITIC  ACID.  555 

bears  to  acetic  aldehyde.  These  formulae  are  supported  by  the 
fact  that,  while  aldehyde  chloral  and  chloral  hydrate  are  all 
converted  by  PO15  into  ethylidene  chloride  (31)  (464),  the 
compound  of  chloral  with  alcohol  yields,  under  the  same  condi- 
tions, a  substance  represented  by  the  symbol  (  OC13-  CH)=Eto^  Cl, 
and  not  the  normal  products  of  the  action  of  PC15  on  chloral 
and  alcohol  separately,  as  we  should  expect  if  they  were  pres- 
ent as  such  in  the  compound  in  question. 

It  has  been  stated  above  that  acetic  chloral  may  be  formed 
from  acetic  aldehyde  by  the  direct  action  of  chlorine  gas  un- 
der regulated  conditions.  It  is  simply  necessary  that  there 
should  be  present  with  the  aldehyde  lumps  of  marble  to  absorb 
the  HCl,  which  is  formed  by  the  reaction ;  for  HGl  converts 
acetic  aldehyde  into  crotonic  aldehyde,  and  this  product  is  then, 
the  only  point  of  attack  for  the  chlorine  gas.  Thus  it  is  that 
when  chlorine  acts  on  acetic  aldehyde  without  any  check,  the 
final  product  is  not  acetic  chloral,  but  a  new  chloral  derived 
from  crotonic  aldehyde  (453). 

( Off,-  V&  Off-  CO)-H  (  C013-  Off=  Cff-  00)- ff. 

Crotonic  Aldehyde.  Crotonic  Chloral. 

Crotonic  chloral  resembles  outwardly  acetic  chloral,  and 
forms  a  similar  compound  with  water.  It  is  the  only  other 
chloral  which  has  thus  far  been  isolated ;  but  an  insoluble  iso- 
meric  modification  of  common  chloral  is  known  whose  relations 
are  not  yet  understood. 

495.  Mellitic  Acid.  —  This  compound  has  long  been  known 
as  a  constituent  of  the  mineral  mellite  or  honeystone,  which 
is  mellitate  of  aluminum,  \_Al^\O60^  .  $ff20,  and  is  found  in 
reddish-yellow  octahedral  crystals  in  the  brown  coal  at  several 
localities  ;  but  it  is  only  recently  that  its  remarkable  chemical 
relations  have  been  discovered.  It  has  been  shown  by  Bayer 
that  this  acid  is  hexabasic  and  belongs  to  the  phenyl  group. 
It  may  be  regarded  as  derived  from  benzol,  C6ffG,  by  replacing 
all  the  six  atoms  of  hydrogen  with  oxatyl.  Benzoic  acid,  it 
will  be  remembered,  is  benzol  with  one  of  the  hydrogen  atoms 
replaced  by  oxatyl,  and  Bayer  has  not  only  been  able  to  iden- 
tify three  of  the  four  intermediate  acids  which  are  theoretically 
possible,  but  he  has  also  shown  that  each  of  the  three  is  capa- 
ble of  two  isomeric  modifications.  Thus  we  have  :  — 


556  MELLITIC  ACID.  [§  495. 


Normal  Series. 
Benzol. 
Benzole  Acid. 
Terephthalic  Acid. 
Trimellitic  Acid. 
Pyromellitic  Acid. 

Isomsric  Series. 

Isophthalic  Acid. 
Trimesic  Acid. 
Prehnitic  Acid. 

2d  Isomeric  Series. 

Phthalic  Acid. 
Hemimellitic  Acid. 
Mellophanic  Acid. 

C6H3=(  CO-Ho~)y 
C6Ha=C  C0-Ho\. 

Mellitic  Acid.  C6  vi 

The  isomeric  modifications  probably  result  from  a  variation  of 
the  order  in  which  the  hydrogen  and  oxatyl  atoms  are  attached 
to  the  carbon  atoms  of  the  primary  nucleus  (428,  Fig.  c.)  and 
(456). 

One  of  the  compounds  included  in  the  above  scheme  has 
certain  other  remarkable  chemical  relations  which  point  with 
great  certainty  to  its  molecular  constitution.  Phthalic  acid 
is  not  only  a  derivation  of  benzol,  but  also  of  naphthaline; 
for  this  well-known  hydrocarbon  (434),  when  heated  with 
strong  oxidizing  agents,  yields  a  mixture  of  phthalic  and  oxalic 
acids.  Assuming  it  proved  that  phthalic  acid  has  the  benzol 
nucleus,  the  best  theory  we  can  form  in  regard  to  this  reaction 
gives  to  the  molecule  of  naphthaline  the  singular  constitution 
represented  below ;  and  it  can  be  seen  by  comparing  the  three 
graphic  symbols  placed  side  by  side  that  the  reaction  is  thus 
fully  explained. 

H 
H  ¥         H  0          H 

<>,      0      H\G  ^     A    .H         A      A     .H 

C  Ntf  \     C          G  0          CO 

C  ,C  /    C          <7  0          0  A$* 

p'    *Q      H  /  c'     %  o  *  ^H          *  C '     ^  G'      H 

H  H         H  0         H 

Oxalic  Acid.  Naphthaline.  Jf 

Phthalic  Acid. 

If  this  theory  is  correct,  it  follows  that  in  phthalic  acid  the 
two  oxatyl  groups  are  united  to  adjacent  carbon  atoms  of  the 
nucleus,  and  that  its  constitution  is  so  far  determined.  Again, 
it  will  be  noticed  that  these  adjacent  carbon  atoms  are  united 
by  a  double  bond,  and  that  in  the  closed  chain,  of  which  they 
are  a  part,  the  links  are  joined  by  double  and  single  bonds  al- 
ternating. Now  it  is  evident  that  if  either  of  these  double 
bonds  could  be  exchanged  for  a  single  one,  the  nucleus  would 


§  4i)j.]  MELLITIG  ACID.  557 

be  able  to  attach  to  itself  two  additional  hydrogen  atoms,  six 
in  all,  and  that  if,  besides,  we  could  break  the  chain  between 
the  two  adjacent  atoms  above  referred  to,  the  nucleus  could 
hold  yet  two  more,  and  we  should  then  have  suberic  acid  (470). 
Now  all  these  transformations  appear  to  be  possible,  for  we 
have  been  able  to  prepare  the  following  series  of  bodies  :  — 

Phthalic  Acid,  O6fff(  COffo)2. 

Hydro-phthalic  Acid,  C6Hf(  COffo)2. 

Tetrahydro-phthalic  Acid,  C^H^GO-So)f 

Hexahydro-phthalic  Acid,  C<&HIQ=(  C0-Ho)2. 

Suberic  Acid,  O6ff12=(  GOHu)2. 

We  are  also  acquainted  with  still  another  derivative  of  benzol 
called  tartro-phthalic  acid,  which  differs  from  hexahydro-phtha- 
lic  acid  only  in  that  there  is  associated  with  each  oxatyl  group, 
and  attached  to  the  same  carbon  atom,  HO  in  place  of  H. 
Tartro,  hexahydro,  and  tetrahydro-phthalic  acids  are  related 
by  a  peculiar  kind  of  homology  to  tartaric  succinic  and  maleic 
acids  respectively,  which  will  be  evident  on  bringing  together 
their  graphic  symbols.  The  theory  that  in  all  these  acids  ex- 
cept suberic  the  two  oxatyl  groups  are  joined  to  adjacent  car- 
bon atoms  is  sustained  by  other  considerations  than  the  one  we 
have  given  here,  but  for  these  we  must  refer  the  student  to  the 
original  memoirs. 

The  graphic  symbol  of  naphthaline  being  so  symmetrical,  it 
would  seem  impossible  to  determine  on  which  side  the  division 
of  the  nucleus  takes  place  in  the  reaction  represented  above  j 
but  there  are  conditions  in  which  even  this  can  be  traced.  We 
have  written  below  the  symbol  of  naphthaline  so  as  to  indicate 
in  a  measure  its  bilateral  structure,  and  on  the  same  line  we 
have  given  the  symbols  of  two  of  its  well-marked  substitution 
products,  which  are  very  numerous  :  — 


Naphthaline.  Dichlordioxynaphthaliue.  Pentachlornaphthaline. 

Now  the  first  of  these  derivatives  when  oxidized  gives  phthalic 
acid  like  naphthaline  itself,  while  under  the  same  conditions  the 
second  gives  tetrachlorphthalic  acid.  Evidently,  then,  in  the 
first  case  the  substitution  is  confined  to  one  side  of  the  naphtha- 
line molecule,  and  the  division  which  accompanies  the  oxida- 
tion takes  place  on  the  same  side  ;  while  in  the  second  case  not 


558  MELLITIC  ACID.  [§495. 

only  all  the  hydrogen  atoms  on  one  side  are  replaced,  but  also 
one  on  the  other,  and  the  division  takes  place  on  the  side  of  the 
single  chlorine  atom ;  for  were  the  nucleus  divided  on  the  other 
side  we  should  have  not  tetrachlorphthalic  but  monochlorphthalic 
acid.  These  reactions,  moreover,  furnish  very  strong  evidence 
in  favor  of  the  theory  of  the  structure  of  the  naphthaline  mole- 
cule stated  above.  Since,  as  we  obtain  a  body  having  the 
structure  of  phthalic  acid  on  whichever  side  we  divide  the 
molecule,  it  is  evident  that  the  two  sides  must  have  the  same 
structure,  so  that  if  we  are  not  mistaken  in  regard  to  the  struc- 
ture of  phthalic  acid  there  can  remain  but  little  doubt  in 
regard  to  that  of  naphthaline.  Now  phthalic  acid,  when  heated 
with  an  excess  of  lime,  yields  benzol,  and  benzol,  when  oxi- 
dized under  certain  conditions,  yields  benzbic  and  phthalic 
acid,  reactions  which  may  be  almost  said  to  prove  that  this 
acid  contains  the  benzol  or  phenyl  nucleus.  The  simple  rela- 
tions of  phthalic  to  benzoic  acid  are  evident. 

If,  with  Kekule,  we  number  the  carbon  atoms  of  the  phenyl 
nucleus  from  1  to  6,  and  assume  that  in  phthalic  acid  the  two 
oxatyl  radicals  are  united  to  the  first  and  second  atoms  of  the 
nucleus,  then  it  is  evident  that,  without  altering  the  general 
structure,  two  modifications  of  it  may  be  obtained  by  changing 
the  position  of  the  oxatyl  radical,  which  can  also  be  attached 
either  to  the  first  and  third  or  to  the  first  and  fourth  atoms  of 
the  closed  chain.  Now  there  is  good  reason  for  believing  that 
such  is  the  position  of  the  radicals  in  isophthalic  and  tere- 
phthalic  acids  respectively,  but  for  the  evidence  we  must  refer 
to  the  original  papers.1 

1  Ann.  Chem.  und  Pharm.,  VII.  Supplementband,  1;  also  CXLIX.  27;  also 
Jour.  Chem.  Soc.  of  London,  Vol.  IX.  372. 


§  496.]  QUINONE.  559 


Quinone  Group. 

496.  Quinone.  —  The  artificial  production  of  alizarine,  the 
coloring  principle  of  madder,  is  not  only  one  of  the  most  re- 
markable achievements  of  modern  chemistry,  but  is  also  a 
direct  corroboration  of  the  validity  of  the  mode  of  reasoning 
which  the  new  philosophy  of  the  science  has  introduced.  Ali- 
zarine was  actually  constructed  by  following  out  the  indications 
of  a  theory  of  its  molecular  structure,  to  which  a  study  of  its 
reactions  and  those  of  allied  compounds  had  led.  In  order  to 
make  clear  the  course  of  the  investigation  we  must  go  back  to 
the  discovery  of  quinone  in  1838.  This  body  was  obtained 
by  the  oxidation  of  quinic  acid,  a  vegetable  acid  found  in  cin- 
chona bark,  where  it  is  combined  with  cinchonine  and  quinine. 
Quinone  is  a  volatile  solid,  crystallizing  by  sublimation  in 
shining  yellow  needles,  which  have  the  composition  indicated 
by  the  empirical  symbol  C^H^O^  When  heated  with  a  mix- 
ture of  hydrochloric  acid  and  potassic  chlorate  it  is  rapidly 
converted  into  tetrachlorquinone,  CQGl^O^  a  compound  which 
is  identical  with  chloranil,  a  product  of  the  action  of  the  same 
agents  on  carbolic  acid,  aniline,  and  other  well-known  bodies 
of  the  phenyl  group.  But  although  these  reactions  indicated  a 
close  relationship  with  the  class  of  compounds  formed  around 
the  carbon  nucleus,  represented  in  Fig.  c.,  page  457,  the  first 
satisfactory  theory  in  regard  to  the  molecular  structure  of 
quinone  was  that  advanced  by  Graebe  in  1868.1  He  concluded, 
as  the  result  of  a  very  extended  investigation  of  the  whole 
class  of  allied  compounds,  first,  that  the  molecule  of  quinone 
contains  the  phenyl  nucleus ;  secondly,  that  the  two  atoms  of 
oxygen  in  this  molecule  are  united  together 
by  a  common  bond,  thus  forming  a  dyad  radi-  , 

cal  which  aids  in  binding  together  two  adja-  ,,  O  s 

cent  carbon  atoms  of  the  phenyl  nucleus,  thus :    H-C  C~0 

so  that,  according  to  his  view,  quinone  may    jj-Q 
be  regarded  as  derived  from  benzol  by  re-  *  C 


placing  two  neighboring  hydrogen  atoms  in 
its  molecules  by  the  radical  =[  02]« 


H 


1  Untersuchungen  iiber  die  Chinongruppe,  Ann.  der  Chem.  und  Pharm., 
CXLVI. 


5GO  QUINONE.  [§  496. 

The  above  conclusions  are  based  chiefly  on  the  following 
facts.  In  support  of  the  first  we  have  a  large  number  of  re- 
actions besides  those  mentioned  above,  whose  concurrent  testi- 
mony leaves  no  doubt  that  the  benzol  and  the  quinone  group 
of  compounds  are  formed  around  the  same  carbon  nucleus,  so 
that  if  we  accept  Kekule's  1  theory  in  regard  to  the  first,  we 
must  extend  it  also  to  the  last.  In  support  of  the  second,  we 
have  the  fact  that  when  by  reactions,  which  are  well  under- 
stood, the  oxygen  of  the  quinone  molecule  is  replaced  by  hy- 
droxyl  or  chlorine,  the  two  atoms  are  exchanged  for  only  two 
atoms  of 'these  monad  radicals,  and  not  for  four,  as  would  be 
the  case  if  the  oxygen  atoms  were  united  to  the  carbon  nucleus 
by  all  four  of  their  bonds.  Thus,  when  quinone  is  acted  on 
by  hydriodic  acid  it  yields  hydroquinone,  whose  symbol  is 
O6fffffo2,  and  oxidizing  agents  change  this  body  back  to  qui- 
none. Again,  when  tetrachlorquinone,  C$C1402,  is  acted  on 
by  phosphoric  chloride  the  products  are  C6C16  and  free  chlorine 
gas.  It  is  impossible,  however,  in  a  few  words,  to  do  justice  to 
the  arguments  which  Graebe  advances  in  support  of  his  theory, 
which  will  be  found  clearly  stated  in  the  paper  already  re- 
ferred to. 

In  studying  the  derivatives  of  quinone  Graebe  recognized 
certain  general  characteristics,  which  he  attributed  to  their 
supposed  molecular  structure.  Of  these,  the  most  striking, 
after  the  two  just  illustrated,  is  the  fact  that  two  of  the  monad 
atoms,  H  or  Cl,  associated  with  the  oxygen  radical,  =[  02],  in 
the  molecular  group  may  be  readily  replaced  by  Ho,  H^N,  or 
JFTSO&  the  product  being  an  acid,  an  amide,  or  a  sulpho-acid. 
This  well-marked  character  of  the  quinone  group  of  compounds 
Graebe  attributes  to  the  influence  of  the  atomic  group  [<7202] 
on  the  rest  of  the  molecule,  which,  as  he  supposes,  throws  the 
neighboring  atoms  into  a  polar  condition,  similar  to  that  pro- 
duced by  CO  in  the  organic  acids  and  aldehydes.  The  three 
characteristics  of  the  quinone  group  we  have  signalized  are 
better  illustrated  by  the  chlorine  derivatives  of  quinone  than 
by  quinone  itself.  Take,  for  example,  tetrachlorquinone  or 

1  Kekul6  originated  the  theory  in  regard  to  the  molecular  structure  of  the 
radical  phenyl  which  has  been  presented  in  this  book.  For  the  evidence  on. 
which  it  is  based  we  must  refer  to  Kekule"'s  well-known  work  on  Organic 
Chemistry,  as  it  is  too  extended  to  be  given  here  ;  also,  Ann.  Chem.  und 
Pharm.,  CXXXVII.  129. 


§  497.]  NAPHTHO-QUINONE.  561 

chloranil,  mentioned  above,  which  has  the  following  chemical 
relations  :  — 

1.  Reducing  agents  readily  convert  chloranil  into  tetrachlor- 
hydroquinone,  C6ClfHo2,  a  compound  which  oxidizing  agents 
as  readily  change  back  to  chloranil,  and  whose  atoms  of  hydro- 
gen may  be  replaced  by  metals  or  organic  radicals,  giving  such 
bodies  as  C6OlfKo^  C^ClfEto^  O6Cl4=Aco2. 

2.  When  acted  on  by  phosphoric  chloride,  chloranil  yields 
O&  C16  and  free  chlorine,  as  stated  above. 

3.  If  chloranil  is  dissolved  in  a  solution  of  potassic  hydrate, 
a  metathesis  takes  place  between  C12  in  the  first  and  Ko2  in  the 
last,  in  conformity  with  the  third  characteristic  we  have  de- 
scribed, and  if  the  proportions  are  rightly  regulated  there  crys- 
tallize out  from  the  solution  red  needles  of  potassic  chloranil- 
ate,  Kof  C6  (7/2=[  02].     From  a  solution  of  this  salt  hydrochloric 
or  sulphuric  acids  precipitate  chloranilic  acid,  /&2=  (76  (74=[  02]» 
in  similarly  colored  crystals. 

Trichlorquinone,  C&CISH0.2,  yields  also  similar  derivatives, 
which  for  the  most  part  contain  C6ClBH'm  place  of  (76074,  but 
when  treated  with  potassic  hydrate  it  yields  chloranilic  acid, 
the  same  product  which  is  obtained  from  tetrachlorquinone, 
showing  that  the  single  remaining  hydrogen  atom  is  one  of  the 
two  replaced  in  the  reaction. 

497.  Naphtho-quinone.  —  Graebe's  next  step,  in  the  course 
of  investigation  we  are  following,  was  to  recognize  in  the  com- 
pound we  have  called  dichlordioxynaphthaline  (495)  a  body 
having  the  same  general  structure  as  quinone.  In  a  paper 
published  in  1869,1  he  showed  that  this  body,  which  he  calls 
dichlornaphtho-quinone,2  has  the  same  general  characteristics  as 
tetra-  or  tri-chlorquinone.  Thus  it  appears, 

1st.  That  dichlornaphtho-quinone,  when  acted  on  by  reducing 
agents,  yields  dichlorhydronaphtho-quinone, 


Moreover,  in    this  compound,  as  in   tetrachlorhydro-quinone, 
ffo2  may  be  replaced  by  Acoz. 

2d.  That  dichlornaphtho-quinone  yields  with  phosphoric  chlo- 
ride the  compound  CwffsCls,  by  which  it  is  evident  that,  as  in 

1  Ann.  der  Chem.  und  Pharm.,  CXLIX. 

2  The  German  name  for  quinone  is  chinon,  ano\  the  names  of  the  different 
quinone  derivatives  are  formed  from  this  root. 

24*  jj 


562  ANTHRAQUINONE  AND  ALIZAEINE.  [§498. 

the  case  of  tetrachlorquinone,  the  group  [  02]  is  replaced  by 
(7/2,  although  at  the  same  time  a  further  replacement  of  the 
hydrogen  atoms  of  the  original  naphthaline  molecule  is  effected 
so  that  no  free  chlorine  is  evolved. 

3d.  That  when  dichlornaphtho-quinone  is  dissolved  in  a  solu- 
tion of  potassic  hydrate  there  are  formed  cherry-red  needles 
of  the  potassic  salt,  of  an  acid  corresponding  to  chloranilic 
acid,  and  from  this  salt,  by  the  action  of  hydrochloric  acid,  the 
acid  itself  is  readily  obtained,  as  a  yellow  precipitate  having 
the  composition  expressed  by  the  symbol  Ho-C^H^Cl^O^]. 
It  will  be  noticed  that  in  the  reactions  by  which  the  so-called 
chloroxynaphthalic  acid  is  formed  only  one  atom  of  chlorine  is 
replaced  by  hydroxyl,  and  not  two,  as  in  the  case  of  chloranilic 
acid.  The  acid  is  a  coloring  matter,  dyeing  wool  a  scarlet  or 
orange  color,  but  has  no  affinity  for  alumina  mordants. 

The  above  facts  certainly  justified  the  theory  of  Graebe 
in  regard  to  the  constitution  of  these  derivatives  of  naphtha- 
line, and  since  his  paper  was  published  naphthoquinone  itself, 
(710^=[02],  has  been  obtained.  Thus  the  word  "quinone"  has 
become  the  name  of  a  class  of  compounds,  and  indicates  the 
peculiar  molecular  structure  we  have  described. 

Dichlornaphtho-quinone  and  chloroxynaphthalic  acid  were 
discovered  by  Laurent,  1836-40,  and  the  great  similarity,  as 
indicated  by  ultimate  analysis,  between  the  last  and  alizarine 
was  noticed  soon  after.  Indeed,  chloroxynaphthalic  acid  was 
for  some  time  regarded  as  chlorinated  alizarine,  and  this  opin- 
ion was  apparently  confirmed  by  the  fact  that  both  these  sub- 
stances yield  phthalic  acid  by  decomposition  with  nitric  acid. 
But  about  six  years  since  Martius  and  Griess  succeeded  in 
replacing  the  single  atom  of  chlorine  in  chloroxynaphthalic 
acid  with  hydrogen,  and  a  coloring  matter  was  obtained  having 
the  formula  C10#603,  which  is  identical  with  that  assigned  to 
alizarine  by  Strecker.  This  body,  however,  did  not  prove  to 
be  alizarine,  although  it  was  supposed  at  the  time  to  be  iso- 
meric  with  it. 

498.  Anthraquinone  and  Alizarine.  —  Graebe,  now  associ- 
ated with  Liebermann,  beginning  the  investigation  of  alizarine 
at  the  point  we  left  it  in  the  last  section,  naturally  inferred, 
from  the  resemblance  to  chloroxynaphthalic  acid,  that  the  col- 
oring matter  of  madder  might  be  a  similar  acid,  though  derived 


§498.]  ANTHRAQUINONE  AND  ALIZARINE.  563 

from  a  different  quinone,  and,  in  order  to  obtain  some  clew  to 
the  hydrocarbon  to  which  it  is  related,  these  chemists  fc sought 
as  a  first  step  to  reduce  natural  alizarine  by  heating  it  with 
powdered  zinc,  adopting  a  method  first  suggested  by  Bayer  for 
reducing  similar  compounds.  The  result  was  a  solid  body, 
which  was  soon  recognized  as  identical  with  anthracene,  a  hy- 
drocarbon (Cnfflo)  associated  with  naphthaline  in  coal-tar,  and 
it  was  of  course  at  once  inferred  that  alizarine  was  the  quinone 
acid  of  this  well-known  hydrocarbon,  thus  :  — 

Ol4ffw  Ol4ff802  ffofC^O,-]. 

Anthracene.  Anthraquinone.  Anthraquinonic  Acid  or  Alizarine. 

The  formula  of  alizarine  thus  deduced,  although  differing  from 
that  of  Strecker,  agreed  with  that  of  Schunk,  who  had  made 
a  most  extended  investigation  of  the  constituents  of  madder. 
Before,  however,  this  theory  of  the  constitution  of  alizarine 
could  be  established,  it  was  essential  to  reverse  the  process  of 
reduction  and  produce  alizarine  from  anthracene,  and  the  first 
step  was  to  obtain  the  anthraquinone.  Here  again  Graebe  was 
aided  by  the  previous  investigations  of  Laurent,  who  long  before 
had  obtained  an  oxygenated  derivative  of  anthracene,  which  he 
called,  in  accordance  with  a  peculiar  nomenclature  of  his  own, 
anthracenuse.  The  substance  had  been  re-examined  by  Ander- 
son, who  gave  it  the  symbol  CUH^O^  and  in  it  Graebe  and  Lie- 
bermann  at  once  recognized  the  required  quinone.  It  only 
now  remained  to  replace  two  atoms  of  the  hydrogen  in  this 
body  by  hydroxyl,  in  order  to  settle  the  question  whether  aliza- 
rine is  the  quinone  acid  of  anthracene  or  not.  The  method 
was  obvious.  Anthraquiuone  was  heated  with  bromine,  which, 
replacing  two  of  its  hydrogen  atoms,  yielded  the  compound 
<714/^flr2=[02],  and  this  heated  to  180°  with  a  solution  of  po- 
tassic  hydrate  gave  an  intense  blue  solution,  from  which  hydro- 
chloric acid  precipitated  a  yellow  crystalline  powder  identical 
in  every  respect  with  the  alizarine  obtained  from  madder. 

This  was  the  first  instance  of  the  artificial  production  of  a 
vegetable  coloring  matter,  and  we  have  dwelt  at  more  length 
than  usual  on  the  history  of  this  beautiful  discovery,  because 
it  affords  an  admirable  illustration  of  the  methods  of  modern 
chemistry.1  Before  the  discovery  could  be  applied  in  the  arts 

1  In  preparing  this  section  we  have  been  aided  by  an  interesting  paper  of 
W.  H.  Perkins  (Journal  of  Chem.  Soc.  of  London,  for  1870,  page  133),  in 
which  specimens  of  prints  made  with  artificial  alizarine  are  given. 


564  CONSTITUTION  OF  ANTHRACENE.  [§500. 

it  was  of  course  essential  that  the  synthetical  process  should 
be  modified  so  as  to  adapt  it  to  a  manufacturing  scale,  and  this 
has  been  in  a  great  measure  accomplished  by  substituting  for 
bromine  sulphuric  acid,  which  when  heated  with  anthraquinone 
converts  it  into  a  sulpho  acid,  (HSOZ)^CUH^\_0^  and  this, 
like  the  corresponding  bromine  compound,  yields  alizarine  when 
heated  with  potassic  hydrate. 

499.  Purpurine.  —  There   is   associated  with   alizarine  in 
madder  a  second  coloring  material  called  purpurine,  but  as  it 
is  not  absorbed  by  mordanted  calicoes  it  has  little  commercial 
value.      Like  alizarine,  it  is  reduced  to  anthracene  by  zinc 
powder,  and  the  result  of  its  ultimate  analysis  agrees  very  well 
with  the  symbol  HofCuH5=[0.>~].  but  we  have  no  further  proof 
-of  its  correctness.     A  third  coloring  principle   has  also  been 
distinguished,    called    pseudopurpurine,    whose    analysis   gave 
results   corresponding  to  the   symbol   Ho^CuHf\_0^\.      It  is 
probable  that  all  three  of  these  coloring  materials  occur  in  the 
madder-root  as  glucosides. 

500.  Constitution  of  Anthracene.  —  We   have  now  distin- 
guished three  quinones,  viz.  benzoquinone,  naphthoquinone,  and 
anthraquinone.     Graebe  and  Liebermann  have  shown  in  their 
recent  paper1  that  the  last  has  the  chief  characteristics  we 
have  distinguished  in  the  other  two,  and  that  it  gives  simi- 
lar derivatives.     It  only  remains  to  add  a  few  works  in  regard 
to  its  molecular  constitution.     In  the  paper  just  referred  to 
Graebe  and  Liebermann  advance  the  theory  that  the  anthracene 
molecule  has  a  structure  which  may  be  represented  thus  :  — 

HG 


EG        V       ffO 

HO         C  C 

<>  /        •*  «          N 

HO         G         HG 
HG.       HG 
HG 

Anthracene. 

and  hence  that  anthracene  bears  the  same  relation  to  naphtha- 
line that  naphthaline  bears  to  benzol  (428)  and  (495).  This 
theory  is  not  only  rendered  probable  by  the  similar  chemical 
relations  of  those  three  hydrocarbons  which  we  have  been 

l  Ann.  der  Chem.  und  Pharm.,  VII.  Supplementband,  1870,  312. 


§500.]  CONSTITUTION  OF  ANTHRACENE.  565 

studying,  but  it  also  furnishes  a  satisfactory  explanation  of  two 
synthetical  processes  by  which  anthracene  has  been  produced. 
1.  When  benzylchloride,  CGff5-  Cff2-  Ol,  is  heated  with  water 
in  a  closed  tube  to  180°,  anthracene  is  one  of  the  chief  pro- 
ducts. If  we  suppose  that  the  production  of  the  hydrocarbon 
results  from  the  coalescing  of  two  molecules  of  the  chloride, 
the  reaction  may  be  indicated  thus  :  — 

HC       HO-H.GI 
HO*      '  '<?'  HC~-H,Cl 


HO       H  H  -  G         HO 

HO         HO 


and  it  can  readily  be  seen  that  if  each  molecule  of  the  chloride 
gives  up  a  molecule  of  HOI  and  an  atom  of  H,  we  shall  have 
the  two  halves  of  a  molecule  of  anthracene  as  represented 
above. 

2.  Anthracene  may  be  also  formed  by  passing  a  mixture  of 
benzol  and  styrol  (cinamene)  vapors  through  a  red-hot  tube, 
and  the  same  graphic  symbol  gives  a  very  simple  account  of 
its  production. 

HO          HO 

j£w^?'  r***        £ 
'^0'  *x        *-?L>? 

HC^        HO 

"HO' 

This  synthesis  was  observed  by  Berthelot,  who  also  obtained 
anthracene  under  similar  conditions  from  toluol  and  also  from 
a  mixture  of  benzol  and  ethylene.  Both  processes  admit  pf  a 
similar  simple  explanation  based  on  the  above  formula.  In 
the  last  case  the  chief  product  is  styrol,  which  probably  pre- 
cedes the  formation  of  anthracene. 

The  three  hydrocarbons,  benzol,  naphthaline,  and  anthra- 
cene, form  a  well-defined  series,  whose  successive  members 
differ  from  each  other,  not,  as  in  the  alcohol  family,  by  CH%  but 


566  CHRYSENE  AND   PYKENE.  [§501. 

by  C4ff2,  and  to  this  corresponds  a  difference  of  about  140°  in 
the  boiling-points. 

06ff6        Diff.         Cinffa        Diff.         Ouff1Q. 
B.  P.    80°          136°          216°         144°  360° 

Apart  from  similar  differences  which  the  gradations  in  the 
series  necessarily  determine,  these  bodies  strikingly  resemble 
each  other  both  in  their  physical  and  chemical  qualities.  The 
last  point  has  been  illustrated  in  this  chapter  so  far  as  regards 
the  formation  of  the  quinone  derivatives,  and  the  impression 
produced  by  the  facts  here  presented  would  be  strengthened  by 
a  further  study  of  the  subject.  All  this  of  course  indicates  a 
similarity  in  the  molecular  structure  of  these  bodies,  and  the 
cumulative  evidence  in  favor  of  the  theory  here  adopted  is 
therefore  much  greater  than  that  which  can  be  obtained  in  re- 
gard to  either  of  the  substances  separately. 

501.  Ghrysene  and  Pyrene.  —  Since  the  identification  of 
anthraquinone  it  has  been  discovered  that  two  other  hydrocar- 
bons associated  with  naphthaline  and  anthracene,  among  the 
least  volatile  of  the  products  of  the  distillation  of  coal-tar, 
were  capable  of  yielding  derivatives  belonging  to  the  class  of 
quinones.  The  names  chrysene  and  pyrene  were  given  by 
Laurent  to  impure  products,  and  it  is  only  very  recently  that 
these  bodies  have  been  isolated  and  their  composition  accu- 
rately determined.1  Chrysene,  C18ff12,  makes  evidently  the 
fourth  term  of  the  naphthaline  series,  differing  from  anthracene 
by  C4ff2,  and  its  molecule  may  be  CH-CH 

regarded  as   formed  from  that  of  * 

anthracene    by    the     addition    of  x  , 

another     phenyl     nucleus,    thus:  fC=  O^ 

Pyrene,   O16ffm  although  not  be-         C&0  OCff 

longing  to  the  same  series,  appears  QJJ  *  C-  Q*  V^ 
to  be  similarly  constituted,  and  *  '  W™/ 

may  be   regarded  as    phenylene- 

naphthaline  ( ClQH6y( C6ff4).  Chryso-quinone,  CWH1J[02'],  has 
the  chief  characteristics  of  a  true  quinone,  but  in  pyrene-qui- 
none,  (716Z^[  02],  the  characters  are  less  strongly  marked. 

1  Graebe  und  Liebermann,  Ann.  Chem.  und  Pharm.,  CLVIIL,  285  and  299. 
June,  1871. 


§502.]   ELECTRICAL  RELATIONS  OF  THE  ATOMS.     567 


Electrical  Measurements. 

502.  Fundamental  Laws.  —  The  following  formulae  express 
the  most  important  properties  of  electrical  currents  :  — 


(1.)  G=F.  (2-)  tf=-  (3-)Q  =  Ct.  (4.)  W  *=&&.(&.)  W=QE. 

The  first  defines  strength  of  current  as  a  magnitude  propor- 
tional to  the  force  which  it  exerts  on  a  magnetic  pole  under 
constant  conditions.  These  conditions  are  the  strength  of  pole, 
w,  the  length'  of  the  conductor,  L,  —  assumed,  as  in  the  com- 
mon form  of  galvanometer,  to  be  bent  in  a  circle  around  the 
pole,  —  and  the  radius  of  this  circle,  K.  The  unit  of  force  is 
that  force  which  imparts  to  one  gramme  of  matter  the  velocity 
of  one  metre  in  one  second,  and  the  unit  pole  that  pole  which 
at  a  distance  of  one  metre  repels  a  similar  and  equal  pole  with 
the  unit  force. 

The  second  is  Ohm's  formula  (88),  and  expresses  the  prin- 
ciple, which  can  be  readily  demonstrated  experimentally,  that 
the  strength  of  current,  as  defined  by  (l),is  directly  propor- 
tional to  the  electromotive  force  of  the  given  circuit,  and  in- 
versely proportional  to  the  resistance  of  the  circuit.  It  also 
involves  the  still  further  truth  that  in  different  parts  of  the 
same  circuit,  where  the  strength  of  current  is  necessarily  the 
same  (88),  the  difference  of  tension  or  potential  l  between  any 
two  points  is  always  proportional  to  the  resistance  between 
these  points. 

The  third  expresses  a  truth  first  verified  experimentally  by 

1  The  influence  of  the  electromotive  force  extends  throughout  the  circuit, 
causing  at  every  cross  section  of  the  conductor  what  we  may  call  an  electrical 
pressure,  which  regulates  the  flow  of  the  electrical  current.  This  pressure  is 
greatest  at  the  surface  of  the  active  plate  where  the  power  originates,  and 
diminishes  as  we  proceed  round  the  circuit  in  either  direction.  At  some 
intermediate  section  where  Jhe  opposite  currents  neutralize  each  other  the 
pressure  is  zero,  and  as  we  move  back  from  this  neutral  point  against  the  neg- 
ative current  we  encounter  an  ever-increasing  "negative  "  pressure,  while  in 
the  opposite  direction  we  meet  an  ever-ir  creasing  "positive"  pressure. 
What  we  here  call  electrical  pressure  is  called  above  tension  or  potential,  and 
without  attempting  to  give  a  theoretical  conception  of  its  nature,  it  is  suffi- 
cient to  say  that  it  is  a  force  measured  at  any  point  of  the  circuit  by  the  ten- 
dency of  the  current  to  leave  the  conductor.  Ohm's  formula  holds  not  only 
for  the  whole  circuit,  but  also  for  any  part  of  it  ;  but  in  such  cases  E  stands, 
not  for  the  whole  electromotive  force,  but  for  the  difference  of  tension  between 
the  two  ends  of  the  portion  under  consideration. 


568  ELECTRICAL  RELATIONS  OF  THE  ATOMS.       [§  504. 

Faraday,  that  the  quantity  of  electricity  which  passes  any 
point  of  a  circuit,  as  measured  by  the  amount  of  electrolysis, 
is  proportional  to  the  strength  of  the  current  and  the  time  dur- 
ing which  it  flows. 

The  fourth  expresses  an  important  law,  first  demonstrated 
experimentally  by  Joule,  that  the  work  done  by  a  current 
(e.  g.  the  quantity  of  heat  generated)  is  proportional  to  the 
square  of  the  current,  to  the  time  during  which  it  acts,  and  to 
the  resistance  which  it  encounters.  It  should  be  remembered 
in  this  connection  that  the  unit  of  force  acting  through  one 
metre  does  the  unit  of  work ;  that  the  force  of  gravity  acting 
on  one  gramme  of  matter  through  one  metre  does  9.8  units  of 
work,  equal  to  one  metre-gramme,  and  that  the  unit  of  heat 
(12)  is  equivalent  to  4157.25  units  of  work  or  423.8  metre- 
grammes. 

The  fifth  is  involved  in  the  previous  three,  from  which  it  is 
readily  deduced,  and  expresses  the  fact  that  the  work  done  in 
any  portion  of  the  circuit  is  proportional  to  the  quantity  of 
electricity  which  passes  over  it  and  to  the  difference  of  ten- 
sion between  the  two  ends. 

503.  Kirchhoff's  Laws.  —  The  following  propositions  may  be 
deduced  from  the  general  theory  of  electrical  currents :  — 

1.  The  sum  of  the  currents  which  approach  any  point  is  al- 
ways equal  to  those  which  recede  from  it. 

Or,  if  we  distinguish  the  first  by  a  plus  and  the  second  by  a 
negative  sign,  we  may  say  more  generally :  — 

The  sum  of  all  the  currents  which  meet  at  a  point  is  equal  to 
zero. 

2.  On  any  continuous  line  of  conductors  the  sum  of  the  pro- 
ducts of  the  resistances  of  the  several  parts  by  the  strength  of  the 
current  in  each  part  is  equal  to  the  sum  of  the  electromotive 
forces  included  in  the  same  closed  circuit. 

The  last  proposition  holds  true  of  every  circuit  which  may 
be  traced  in  any  system  of  conductors  and  batteries,  however 
complicated  the  maze ;  only  currents  flowing  in  opposite  direc- 
tions, with  reference  to  the  given  circuit,  must  be  distinguished 
by  opposite  signs.  Moreover,  the  sum  is  equal  to  zero  when 
there  is  no  electromotive  force  on  the  line  of  conductors  under 
consideration. 

504.  Electrical  Units.  —  In  the  following  problems  the  val- 


§503.]       ELECTRICAL  RELATIONS  OF  THE  ATOMS.  569 

ties  (7,  R,  or  r  and  E  of  Ohm's  formula  are  assumed  to  be 
measured  in  terms  of  the  following  units :  First,  the  unit  of 
current  is  that  which  would  produce,  by  the  electrolysis  of  wa- 
ter, 1  c.  m.8  of  hydrogen  and  oxygen  gas  (measured  under 
standard  conditions)  in  one  minute.  Secondly,  the  unit  of  re- 
sistance is  that  offered  by  a  pure  silver  or  copper  wire  1  m. 
long,  and  1  m.  m.  in  diameter  at  0°.  Lastly,  the  unit  of  elec- 
tromotive force  is  that  which  transmits  a  unit  current  against  a 
unit  resistance  in  a  unit  of  time. 

By  means  of  the  magnetic  and  thermal  relations  given  by 
(1)  and  (4)  above,  it  is  possible  to  express  the  values  of  the 
three  elements  of  an  electrical  current  in  terms  of  the  funda- 
mental units  of  space,  weight  and  time,  the  metre,  the  gramme, 
and  the  second.  The  following  formulae  in  which  L  =  length, 
M  —  mass  or  weight,  and  T '=  time,  are  easily  deduced,  in- 
volving only  simple  mechanical  principles  :  — 

Velocity  =  y=^. 

MV       ML 
Force  =  F=  -^-  =  -^ 

Work  =  W=  FL  =  ^. 

Work  in  metre-grammes  =  -™-.     r-r. 

J.          9*o 

Strength  of  pole  *  =  m  =  — ™ — . 

Strength  of  current 2  =  C=     T    . 

Quantity  of  electricity  =  Q  =  CT  = 

W 
Electro-motive  force  =  E  =  -~-  = 

Resistance  =  #  =  ?=:£=  K 

The  values  of  C,  R,  and  E,  when  the  several  factors  in  Jjie  for- 
mulae expressing  their  values  are  each  taken  equal  to  unity, 
are  called  the  electromagnetic  units.  Thus  the  unit  of  resist- 

1  This  value  is  readily  obtained  by  considering  that  the  force  exerted 
between  the  two  poles  must  be  F  =  —^  or  =  ^,  when  the  two  poles  are 

equal.     Hence,  m  —  D  V  F. 

2  Readily  derived  from  value  of  C,  (1). 


570  ELECTRICAL  RELATIONS  OF  THE  ATOMS.        [§504. 

ance  is  a  velocity  of  one  metre  a  second.1  These  absolute 
units,  however,  are  of  an  order  of  magnitude  which  is  unsuit- 
able for  ordinary  measurements,  but  the  following  very  small 
multiples  or  submultiples  may  be  used  to  advantage :  — 

For  R  the  Ohm  equal  to  107  absolute  units  of  resistance. 

"  "  "  Megohm  '*  '*  lO1^  "  "  "  " 

"  "  »  Microhm  "  "  10  «  "  "  " 

"  E  "  Volt  "  "  105  «  «  «  electromotive  force. 

"  «  "  Megavolt  "  "  1QU  "  "  "  "  " 

"  «  «  Microvolt  "  "  10-1  «  «  u  u  « 

"  C  "  Farad  "  "  10-»  "  "  "  quantity  per  second. 

"  "  "  Megafarad  "  "  10~^  "  «»  "        "          "         " 

"  "  "  Microfarad  "  "  10-"  "  "  "        "          »         « 

The  unit  current  is  a  current  of  one  Farad  a  second. 

A  pure  copper  or  silver  wire  1  m.  m.  in  diameter  and  48.61 
metres  long  has  a  resistance  of  one  Ohm  at  65°  F.,  and  the 
Committee  of  the  British  Association  on  Electrical  Standards 
have  carefully  constructed  a  standard  Ohm  of  which  copies  are 
readily  accessible.  Further,  we  have  a  closely  approximate 
standard  of  electromotive  force  in  the  Daniell's  cell,  which,  ac- 
cording to  Sir  W.  Thompson,  is  equal  to  1.079  Volts,  or  1 
Volt  =  0.9268  of  force  of  Daniell's  cell.  One  Volt  equals 
about  500.6  of  the  old  units,  and  a  current  of  one  Megafarad 
per  second  will  yield  during  one  minute  by  the  electrolysis  of 
water  10.3  c.  m.8  of  gas  very  nearly. 

The  admirable  instruments  now  constructed  for  the  purpose 
enable  us  to  use  the  B.  A.  units,  as  they  are  called,  with  great 
facility,  but  in  solving  the  following  problems  the  older  system 
will  be  found  more  convenient.  The  student,  however,  should 
familiarize  himself  with  both  ;  but  he  should  bear  in  mind  that 
values  in  Ohm's  Volts  and  Farads  must  be  reduced  to  absolute 
units  before  they  can  be  substituted  for  <7,  7?,  or  E  in  Ohm's 
formula. 

Questions  and  Problems. 

1.  What  resistance  does  the  current  suffer  in  an  iron  wire  50  me- 
tres long  and  5  m.  m.  diameter?     Sp.  R.  of  iron  7. 

+  Ans.  14  units. 

2.  Assuming  that  the  Sp.  R.  of  copper  is  1.3  and  that  of  iron  7, 
what  must  be  the  diameter  of  an  iron  wire  which  will  oppose  no 
greater  resistance  to  the  current  than  a  copper  wire  of  2  m.  m.  diam- 
eter?  Ans.  4.64  m.  m. 

1  For  the  interpretation  of  this  remarkable  analytical  result  see  pamphlet 
by  the  author  on  Absolute  System  of  Electrical  Measurements. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS.     571 

3.  It  is  found  by  experiment  that  a  wire  of  German  silver,  7.201 
m.  long  and  1.5  m.  m.  diameter,  opposes  the  same  resistance  to  the 
current  as  a  wire  of  pure  silver  10  m.  long  and  \  m.  m.  diameter. 
What  is  the  Sp.  R.  of  German  silver.  Ans.  12.5. 

4.  It  is  required  to  make  with  132.8  grammes  of  pure  silver,  a 
wire  which  will  offer  a  resistance  of  81  units.     What  must  be  its 
length  and  diameter  ?     Sp.  Gr.  of  silver  =  10.57. 

Solution.     Representing  by  x  the  length  in  metres,  and  by  y  the 

diameter  in  millimetres,  we  deduce  by  [1]  tf  x  —  10.57  =  132.8  and 
by  the  laws  of  conduction  ^  =  81.  Whence  x  =  36  m.  and  y  =' 
|  m.  m. 

5.  What  is  the  length  and  diameter  of  an  iron  wire  weighing 
97.38  grammes,  which  offers  a  resistance  of  9,072  units  ?   It  is  known 
that  the  Sp.  Gr.  of  theJron  =  7.75  and  its  Sp.  R.  =  7. 

Ans.  Length,  144  m.      Diameter,  £  m.  m. 

6.  From  a  given  wire  there  are  four  branches,  of  which  the  re- 
sistance is  respectively  10,   20,  30,  and  40.      Required   the   total 
resistance  when  the  current  passes  simultaneously  through  the  four 
branches. 

Solution.  The  resistance  in  the  first  branch  may  be  represented 
by  a  normal  silver  wire  10  m.  long  and  1  m.  m.  diameter.  If  we 
call  the  area  of  a  transverse  section  of  this  wire  s,  then  the  resist- 
ance in  the  other  three  branches  will  be  represented  by  normal  wires 
of  the  same  length,  but  having  on  the  cross  sections  the  areas  £  s, 
^s  and  ^s  respectively.  If  next  we  conceive  of  these  wires  as 
merged  in  one,  having  the  common  length  10m.  and  an  area  on  the 
section  equal  to  (1  -f-  \  -\-  %  -f-  J)  s,  it  is  evident  that  such  a  wire 
will  represent  the  resistance  required.  Hence  we  easily  deduce, 

Ans.   4.8. 

7.  A  closed  circuit  has  two  branches  through  which  the  current 
passes  simultaneously.     In  one  branch  r  =  100.     What  length  of 
copper  wire  5  m.  m.  diameter  must  be  used  for  the  other  that  the 
total  r  =  50  ?  ;  Ans.  2,500  metres. 

8.  A  conductor  has  two  branches,  one  having  r  =  756,  the  other 
so  adjusted  that  when  the  current  passes  at  the  same  time  through, 
both,  the  total  resistance  equals  540.     Required  the  length  of  a  Ger- 
man silver  wire  \  m.  m.  diameter  and  Sp.  R.  =  12.5,  which,  when 
inserted  in  the  adjusted  branch,  will  increase  the  total  resistance  to  630. 

Solution.  By  principle  of  last  problem  we  easily  find  that  the 
resistance  in  the  adjusted  branch  before  insertion  equals  1,890,  and 
after  insertion,  3,780.  The  difference  between  these  values,  1,890-,. 
is  the  resistance  due  to  the  inserted  wire.  Hence  its  length  must  ba 
37.8  metres. 


572     ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

9.  We  have  a  battery  of  six  Daniells  cells,  in  each  of  which 
.#=475,  JK  =  15,  and  the  external  resistance  against  which  the 
battery  is  to  work,  r  =  10.     The  cells  may  be  arranged,  1st,  as  six 
single  elements ;  2d,  as  three  double  elements ; l  3d,  as  two  three-fold 
elements ;  4th,  as  one  six-fold  element.    Required  the  current  strength 
in  each  case.  Ans.  28.5,  43.8,  47.5  and  38.0  respectively. 

10.  We  have  a  battery  of  twelve  Grove  cells,  in  each  of  which 
E  =  830,  and  .R  =18,  to  work   against  an   external  resistance  of 
r  =  24.     Required  the  strength  of  current  when  the  cells  are  ar- 
ranged, 1st,  as  twelve  single ;  2d,  as  six  two-fold  ;  3d,  as  four  three- 
fold ;  4th,  as  three  four-fold ;  5th,  as  two  six-fold,  and  6th,  as  one 
twelve-fold  element. 

Ans.  41.5,  63.8,  69.2,  66.4,  55.3,  and  32.5  respectively. 

11.  With  a  single  cell,  where  E  and  R  have  a  constant  value, 
what  is  the  maximum  strength  of  current^tnd  under  what  condi- 
tions would  it  be  obtained  ? 

TTI 

Ans.  -^,  when  the  external  resistance  is  nothing. 

12.  With  n  cells  in  each  of  which  E  and  R  have  the  same  value, 
what  is  the  maximum  strength  of  current,  and  under  what  condi- 
tions would  it  be  obtained  ? 

rr 

Ans.  n  £ ,  when  the  cells  are  arranged  as  one  n-fold  element, 
and  work  against  no  external  resistance. 

13.  With  n  cells  as  above,  working  against  a  given  external  resist- 
ance r,  how  should  they  be  arranged  so  as  to  obtain  the  maximum 
value  of  C  ? 

Ans.  So  as  to  make  the  internal  resistance  equal  to  that  of  the 
external  circuit. 

Solution.  If  x  represents  the  number  of  compound  elements  formed 
with  the  n  cells  when  C  in  Ohm's  formula  is  a  maximum,  we  should 
evidently  have  under  this  condition  x  compound  elements,  each 

formed  ©f  -  cells.     The  electromotive  force  of  such  an  arrangement 

would  be  x  E.     The  internal  resistance  would  be  xR  —  -=~  R 

'    x        n 

(compare  problems  8  and  9),  and  the  strength  of  the  maximum 
current  required, 

o=   XE 


*  By  double  elements  is  meant  a  group  of  two  cells  coupled  for  quantity 
(§89)  and  equivalent  to  a  large  cell  having  plates  of  twice  the  size.  Six 
double  elements  are  six  such  groups  arranged  for  intensity,  and  the  other 
terms  have  a  similar  meaning. 


ELECTRICAL   RELATIONS   OF   THE  ATOMS.  573 

The  first  differential  coefficient  of  this  function  of  x  when  C  is  a 
maximum  must  be  equal  to  zero.     Hence, 


or  r=-  *  R. 

n 

That  is,  the  strength  of  the  current  is  at  its  maximum  when  the  in- 
ternal equals  the  external  resistance,  as  stated  above.  Those  who 
are  not  familiar  with  the  elementary  principles  of  the  differential 
calculus  may  satisfy  themselves  of  the  truth  of  this  result  by  com- 
paring the  answers  obtained  to  problems  8  and  9. 

14.  We  have,  in  the  first  place,  for  a  single  cell  of  a  given  combi- 

r» 

nation  working  against  a  feeble  resistance,  the  value  C  =  p  ; 
in  the  second  place,  for  n  cells  of  the  same  combination  working 

against  n  times  the  resistance,  the  identical  value  C  =     J1  .  -  .  In 

n  H  -\-  nr 

"strength"  the  two  currents  are  equal,  but  are  they  identical? 

15.  In  a  given  cell  E  =  475  ;   R  =  15.      The  current  passes 
through  30  metres  pure  copper  wire  2  m.  m.  diameter.     It  is  re- 
quired to  arrange  8  cells  so  that  C  may  be  the  greatest  possible. 

Ans.  They  should  be  arranged  as  two  four-fold  elements. 

16.  We  have  a  battery  of  four  Bunsen  cells  (E  =  800,  R  =  4 
each),  coupled  as  four  single  elements.    The  circuit  is  closed  through 
500  grammes  of  pure  copper  wire.     Required  the  greatest  strength 
of  current,  and  the  dimensions  of  the  wire  that  this  maximum  may 
be  obtained. 

17.  A  simple  Voltaic  cell,  whose  electromotive  force  E  is  known, 
working  against  an  unknown  total  resistance  R'  (both  external  and 
internal),  produces  a  given  effect  upon  a  galvanometer.     Another 
cell  differently  constructed,  working  against-  a  total  resistance  R", 
also  unknown,  produces  the  same  effect  upon  the  galvanometer.     It 
is  also  observed  that  a  measured  length  I  of  normal  copper  wire,  in- 
serted in  the  first  circuit,  produces  on  the  galvanometer  the  same 
difference  of  effect  as  a  length  I'  inserted  in  the  second  circuit. 
Required  the  electromotive  force  E'  of  the  second  cell. 

Solution.  We  easily  deduce  from  Ohm's  formula  the  two  equations 

=        and      --  =     f  whence  we  obtain,— 


Ans.  E'  =  E. 


574     ELECTRICAL  RELATIONS  OF  THE  ATOMS. 

18.  In  order  to  determine  the  electromotive  force  of  a  Bunsen's 
cell,  it  was  compared,  as  in  last  problem,  with  a  Daniell's  cell  whose 
electromotive  force  was  known  to  be  470.     After  adjusting  the  ex- 
ternal resistances  so  that  both  produced  the  same  effect  upon  the 
galvanometer,  it  was  found  that  the  insertion  of  5.6  m.  of  copper 
wire  into  the  first  circuit  caused  the  same  change  in  the  instrument 
as  the  insertion  of  3.29  metres  of  the  same  wire  in  the  circuit  of  the 
Daniells  cell.     What  was  the  electromotive  force  sought  ? 

Ans.  800. 

19.  A  battery  of  40  Bunsen's  cells  remains  closed  for  an  hour,  and 
during  that  time  furnishes  a  current  whose  strength  C  =  30.     How 
much  zinc  will  be  consumed  in  this  time,  assuming  that  there  is 
no  local  action  ? 

Solution.  Such  a  current  would  produce,  by  the  electrolysis  of 
water,  30  c.  m.8  of  gas  in  one  minute,  or  1.8  litres  in  one  hour.  Of 
this  gas  1.2  litres  or  1.2  criths  would  be  hydrogen.  The  chemical 
equivalent  of  zinc  being  32.6,  the  amount  of  zinc  dissolved  in  each 
cell  must  be  1.2  X  32.6  =;  39.12  criths,  and  in  the  forty  cells 
1564.8  criths,  equal  to  140  grammes,  the  answer  required. 

20.  In  an  electrotype  apparatus,  Fig.  85,  16.36  grammes  of  cop- 
per were  deposited  on  the  negative  mould  in  24  hours.     What  was 
the  strength  of  current  ?  Ans.  6  units. 

21.  In  an  electrotype  apparatus  the  electromotive  force  of  the 
single  cell  employed  is  420,  and  the  internal  resistance  5.     The  ex- 
ternal resistance,  including  decomposing  cell,  is  0.25.     How  much 
copper  will  be  deposited  on  the  negative  mould  in  one  hour,  and 
how  much  zinc  will  be  dissolved  in  the  battery  during  the  same 
time  ?         Ans.  9.088  grammes  copper  and  9.346  grammes  of  zinc. 

22.  Thirty-two  Grove  cells   (E  =  830,  R  ==  20  each)  are  con- 
nected as  4  eight-fold  compound  elements  and  the  current  employed 
to  work  an  electro-silvering  apparatus,  in  which  the  total  resistance 
external  to  the  battery  was  equivalent  to  10.     Required  the  number 
of  grammes  of  silver  deposited  each  hour,  and  the  number  of  grammes 
of  zinc  dissolved  during  the  same  time  in  the  battery. 

Ans.  64.24  grammes  of  silver  and  77.56  grammes  of  zinc. 

23.  Assuming  that  the   external  resistance  cannot  be  changed, 
could    the  same  number  of  cells  of  the  battery  described  in  last 
problem  be  so  arranged  as  to  deposit  more  silver  in  the  same  time  ? 

Ans.  They  could  not. 

^  Could  they  be  so  arranged  as  to  deposit  the  same  amount  of  silver 
with  less  expense  of  zinc  ?  What  would  be  the  most  economical  ar- 
rangement, and  under  these  conditions  how  much  silver  would  be 
deposited  in  one  hour  and  how  much  zinc  dissolved  ? 

Answer  to  last  question,  30.25  grammes  silver,  and  9.13  grammes 
of  zinc. 


ELECTRICAL  RELATIONS  OF  THE  ATOMS. 


575 


K  -&-^A 


24.  What  is  the  current  through  25  Ohm  with  a  tension  of  5 

Volts? 

ft*  ^    y    1  O^ 

Ans.  C  =  jj  — =  0.5  X  10~*  or  0.5  Megafarad. 

25.  What  is  the  work  done  by  a  current  of  5  Megafarads  per  sec- 
ond through  a  resistance  of  10  Ohms? 

Ans.   W  =  C^Rt  =  (5  X  10~2)2  X  10  X  107  =  250,000  units 
per  second. 

26.  What  is  the  work  done  by  one  thousand  Farads  in  falling  in 
tension  one  Volt  ? 

Ans.  W=QE=  1000  X  10-8  X  105  =  1000  X  lO^5  =  1  unit 
of  work.     Hence,  9,800  Voltfarads  equal  one  metregramme. 

27.  What  would  be  the  answers  to  Problem  10  in  B.  A.  units? 
Assuming  that  nine  tenths  of  the  external  resistance  is  in  a  coil  of 
platinum  wire   surrounded   by  a  kilogramme   of  water,  how  high 
would  the  temperature  of  the  water  be  raised  in  ten  minutes  ? 

28.  Assuming  that  in  the  system 
of  conductors  represented  in  Fig.  3, 
E  represents  the  electromotive  force 
of  the  voltaic  element,  R  the  total 
resistance  of  the  main  conductor  a  E 
b,  Rl  and  Rt  the  resistances  of  the 
two  conductors  into  which  the  main 
stream  divides,  find  the  values  of  the 

three  corresponding  currents  C,  Cv  and  C2  in  terms  of  E,  R,  Rv 
and  Ry     Prove  also  that   C\  :  C2  =  R2  :  Rlt   and  further,   that 

Cj  =  Cj: — ^-75-  or  Ca  =  Cj; — ^~p-  Lastly,  show  that  the  equiva- 
lent resistance  of  any  number  of  branches  may  be  found  by  adding 
together  the  reciprocals  of  each  branch  and  taking  the  reciprocal  of 
this  sum.  A  conductor  like  72,, 
which  diverts  a  portion  of  the  main 
current  from  Rv  is  called  a  shunt, 
and  if  Rl  is  the  coil  of  a  galva- 
nometer the  galvanometer  would 
be  said  to  be  shunted  by  R#  and 
by  adjusting  the  value  of  R^  to  R^ 
we  can  cause  a  known  fraction  of 
the  whole  current  to  pass  through 
the  instrument. 

29.  In  the   system  of  conductors   represented  in  Fig.  4,  called 
Wheatstone's  bridge,  no  current  passes  over  the  bridge  between  c 
and  d  when  Rl  :  R2  =  R3  :  Rt.    Prove  the  truth  of  this  proposition, 


V  Fio.3. 


;>!  -r>6' 
l^l? 


576 


ELECTRICAL  KELATIONS  OF  THE  ATOMS. 


and  show  how  it  may  be  applied  for  measuring  resistances  when 

we  have  a  set  of  standard  resistance 
coils. 

30.  In  the  system  of  conductors, 
represented  in  Fig.  5,  prove  that  no 
current  passes  in  the  portion  a  El  b 

when  —  =  ,  and  consider 

E          H  +  /i0 

how  the  system  may  be  used  for 
comparing  the  electromotive  force 
of  different  cellg. 


TABLE    I. 

FRENCH    MEASURES. 
Measures  of  Length. 


1  Kilometre 

= 

1000 

Metres. 

I 

Metre 

= 

1.000 

Metre. 

1  Hectometre 

= 

100 

K 

1 

Decimetre 

= 

0.100 

it 

1  Decametre 

= 

10 

tt 

1 

Centimetre 

= 

0.010 

« 

1  Metre 

= 

1 

tt 

1 

Millimetre 

—  • 

0.001 

M 

Ar.  Co.  Log. 
0.2066  188 


Logarithms. 

1  Kilometre        =        0.6214  Mile.  9.7933  712 

1  Metre  =        3.2809  Feet.  0.5159  930  9.4840  070 

1  Centimetre      =        0.3937  Inch.  9.5951  742  0.4048  258 

The  metre  is  one  ten-millionth  of  a  quadrant  of  the  globe. 


Measures  of  Volume. 

1  Cubic  Metre  m:3    =    1000.000  Litres. 

1  Cubic  Decimetre      dHn.3    =          1.000      " 
1  Cubic  Centimetre    cTm:3    =          0.001       " 


Logarithms.  Ar.  Co.  Log. 

Cubic  Metre           =  35.31660  Cubic  Feet.  1.5479790  8.4520210 

Cubic  Decimetre    =  61.02709  Cubic  Inches.  1.7855226  8.2144774 

Cubic  Centimetre  =    0.06103       "        "  8.7855226  1.2144774 

Litre                         =    0.22017  Gallon.  9.3427581  0.6572419 

Litre                         =    0.88066  Quart.  9.9448  083  0.0551  917 

Litre                   .    =    1.76133  Pints.  0.2458  407  9.7541  593 


FRENCH    WEIGHTS. 


1  Kilogramme    =  1000  Grammes. 
1  Hectogramme  =100          " 
1  Decagramme  =10          " 
1  Gramme          =1          " 


1  Gramme  =  1.000  Gramme. 

1  Decigramme  =0.100  " 
1  Centigramme  =  0.010  " 
1  Milligramme  =  0.001  " 


Logarithms.  Ar.  Co.  Log. 

1  Kilogramme  =    2.20462  Pounds  Avoirdupois.    0.3433  337  9.6566  663 

1  =    2.67922       "        Troy.  0.4280083  9.5719917 

1  Gramme        =  15.43235  Grains.  1.1884321  8.8115679 


1  Crith 


0.089578  Grammes. 


8.9522  014     1.0477  986 


TABLE  II. 


ELEMENTARY    ATOMS. 


Perissad 
Elements. 

Atomic 
Weights. 

Symbols 
of 
Molecules. 

Quantiva- 
lence. 

Artiad 
Elements. 

Atomic 
Weights. 

1"! 
*  i 

Quanti  va- 
lence. 

lydrogen 

1.0 
19.0 
35.5 
80.0 
127.0 
7.0 
23.0 
39.1 
85.4 
133.0 
108.0 
204.0 
197.0 
11.0 
140 
31.0 
75.0 
122.0 
210.0 
51.37 
120.0 
94.0 
182.0 

H-H 
F-F 

Cl-Cl 
Br-Br 
I-I 
Li-Li 

Na-Na 
K-K 
Rb-Rb 
Cs-Cs 
Ag-Ag? 
Tl-Tl? 
Au=Au? 

B=B? 

N=N 

M2 

As^Ast 

S6.J6V 
BiJBtf 

F=F? 
U=U? 

Cb^Cb? 
TalTa? 

I 

(i 
tt 
ft 
« 
i 
« 
i 

« 

I  or  III 

III 

« 

III  or  V 

« 
u 

it 
(i 
n 

V 

« 

Copper 
VIercury 

63.4 
200.0 
40.0 
87.6 
137.0 
207.0 
24.0 
65.2 
72.0 
112.0 
9.3 
61.7 
112.6 
92.0 
93.6 
95.0 
588 
58.8 
55.0 
56.0 
52.2 
27.4 
104.4 
199.2 
104.4 
196.0 
106.6 
197.4 
50.0 
118.0 
89.6 
231.4 
28.0 
12.0 

Cu? 
Hg 
Ca? 
Sr? 
Ba? 
Pb? 

21 

In? 
Cd 
G? 
Y? 
E? 
Ce? 
La? 
D? 
Ni? 
Co? 
Mn? 
Fe? 
Cr? 
All 
Ru? 
Os? 
Rh 
lr? 
Pd? 
Pt? 
Ti? 
Sn? 
Zr? 
Th? 
Si? 
C? 

II 

«« 

« 
tt 

a 
ti 

« 

ft 
if 
ft 
tt 

ft 
ft 
n 

II  or  IV 

« 

ft 

ft 

ft 
tt 

H 
tt 

tt 
ft 

IV 

« 
ft 
t« 

fluorine 
Chlorine 
Bromine 
Iodine 

Calcium 
Strontium 
Barium 
Lead 

Lithium 
Sodium 
Potassium 
Rubidium 
Ccesium 

Vlagnesium 
Zinc 

Indium 
Cadmium 

Silver 

Glucinum 
Yttrium 
Erbium 

Thallium 
Gtold           ~ 

Boron 

Cerium 
Lanthanum 
Didymium 

Nitrogen 
Phosphorus 
Arsenic 
Antimonv 

Nickel 
Cobalt 

Bismuth 

Manganese 
Iron 

Vanadium 

Uranium 

Chromium 
Aluminum 

Columbium 
Tantalum 

Ruthenium 
Osmium 

Artiad 
Elements. 

16.0 
32.0 
79.4 
128.0 
96.C 
184.C 

0-0 

S--S 
Se=Se 
Te=Te 
Mo? 
W? 

II 

II  or  VI 
«( 
i< 

VI 

M 

Rhodium 
Iridium 

Palladium 
Platinum 
Titanium 
Tin 

Oxygen 

Sulphur 
Selenium 
Tellurium 

Zirconium 
Thorium 

Molybdenum 
Tungsten 

Silicon 

Carbon 

TABLE    III. 


Specific  Gravity  of  Gases  and  Vapors. 


Names. 

Symbols. 

Air  =  1. 

Sp.Gr. 
H-H=l. 

Half 
Molecular 
Weight. 

Loga- 
rithms. 

Air 

1.000 

14.43 

1.1593 

Hydrogen 

H-H 

0.0693 

1.00 

1.00 

0.0000 

Acetylic  Hydride  (Aldehyde) 

C2H30-H 

1.532 

22.10 

22.00 

1.3424 

Ace  ty  lie  Chloride 

C2H^  O-Cl 

2.87 

41.42 

39.25 

1.5938 

Acetic  Anhydride 

(C2H30)2=0 

3.47 

50.07 

61.00 

1.7076 

Acetic  Acid 

H-O-C2H3O 

2.083 

30.07 

30.00 

1.4771 

Aluminic  Chloride 

[Al2]iCl6 

9.34 

134.80 

133.90 

2.1268 

Aluminic  Bromide 

[Alo]  l-Br6 

18.62 

268.70 

267.40 

2.4272 

Aluminic  Iodide 

[A~12]\I6 

27. 

389.60 

408.40 

2.6111 

Antimonious  Chloride 

sb=aa 

7.8 

112.70 

114.20 

2.0577 

Triethylstibiue 

(  C2H5)3=Sb 

7.23 

104.40 

104.50 

2.0191 

Arsenic 

Ai^Aik 

10.6 

153.00 

150.00 

2.1761 

Arseniuretted  Hydrogen 

H3=As 

2.695 

38.90 

39.00 

1.5911 

Triethylarsine 

(  C2H-)3=As 

5.29 

76.35 

81.00 

1.9085 

Kakodyl 

(  CH3).2As-(  CH3)2As 

7.10 

102.50 

105.00 

2.0212 

Arsenious  Chloride 

As  =  C13 

6.3 

90.90 

90.75 

1.9578 

Arsenious  Iodide 

As=23 

16.1 

232.40 

228.00 

2.3579 

Bismuthous  Chloride 

Bi  =  Cla 

11.35 

163.90 

158.25 

2.1994 

Boric  Methide 

(CH3)3=B 

1.931 

27.90 

28.00 

1.4472 

Boric  Ethide 

(C  H-)  -B 

3.401 

49.10 

49.00 

1.6902 

Boric  Fluoride 

JS=jP3 

2.37 

34.20 

34.00 

1.5315 

Boric  Chloride 

B=Cl 

3.942 

56.85 

58.75 

1.7690 

Boric  Bromide 

B=Br3 

8.78 

126.80 

125.50 

2.0986 

Methylic  Borate 

(CH3)3  =  O^=B 

3.59 

51.80 

52.00 

1.7160 

Ethylic  Borate 

(CZH5)3=63=B 

5.14 

74.20 

73.00 

1.8633 

Bromine 

B>-Br 

5.54 

79.50 

80.00 

1.9031 

Hydrobromic  Acid 

H-Br 

2.71 

39.10 

40.50 

1.6075 

Carbonic  Tetrachloride 

C=Clt 

6.415 

78.14 

77.00 

1.8865 

Marsh  Gas 

CH 

0.5576 

8.05 

8.00 

0.9031 

Phosgene  Gas 

CIO,  C12 

3.399 

49.06 

49.50 

1.6946 

Dicarbonic  Hexachloride 

[C-C]  =  CIK 

8.157 

117.70 

118.50 

2.0737 

Dicarbonic  Tetrachloride 

[C=C]^Cl1i 

5.82 

84.00 

83.00 

1.9191 

Dicarbonic  Bichloride 

[  C=  C]  =  Clt 

47.50 

1.6767 

Carbonic  Oxide 

c=o 

0.967 

13.95 

14.00 

1.1461 

Carbonic  Anhydride 
Carbonic  Sulphide 

CiO, 
CIS, 

1.529 
2.645 

22.06 
38.17 

22.00 
38.00 

13424 
1.5798 

Chlorine 

Cl-Cl 

2.44 

35.22 

35.50 

1.6502 

Hydrochloric  Acid 

H-Cl 

1.27 

18.32 

18.25 

1.2613 

Chromic  Oxychloride 

Cr  =  0»  C7, 

5.5 

79.40 

77.6 

1.8935 

Columbic  Chloride 

CbiCls 

9.6 

138.60 

135.70 

2.1326 

Columbic  Oxychloride 

C6|O,  CZj 

7.9 

114.00 

108.20 

2.0342 

Cyanogen 

CN-CN 

1.806 

26.06 

26.00 

1.4150 

Hydrocyanic  Acid 

H-CN 

0.947 

13.67 

13.50 

1.1303 

Ethyl 

C  H-C  H 

2.0 

28.86 

29.00 

1.4624 

Ethylic  Chloride 

(C2Hb)~Cl 

2.219 

32.02 

32.25 

'1.5085 

Ethylic  Oxide  (Ether) 
Ethvlic  Hydrate  (Alcohol) 

<•$$% 

2.686 
1.613 

37.32 
23.28 

37.00 
23.00 

1.5682 
1.3*517 

TABLE    III.     (Continued.) 


Names. 

Symbols. 

^p.(5r. 

Air  =1. 

Sp.Gr. 
H-H=I. 

Half 
Molecular 
Weight. 

Loga- 
rithms. 

Ethylene  (Olefiant  Gas) 

C2Ht 

0.978 

14.11 

14.00 

1.1461 

"    Chloride  (Dutch  Liq.) 

(C2H4)  =  aa 

3.443 

49.69 

49.50 

1.6946 

Ethylene  Oxide 

(C2Ht)  =  0 

1.422 

20.52 

22.00 

1.3424 

Ethylene  Hydrate  (Glycol) 

(C2Ht)  =  Ot=Ha 

31.00 

1.4914 

Ferric  Chloride 

[Fe2]lClQ 

11.39 

164.40 

162.60 

2.2108 

Iodine 

I-I 

8.716 

125.90 

127.00 

2.1038 

Hydriodic  Acid 

H-I 

4.443 

64.12 

64.00 

1.8062 

Mercury 

Hg 

6.976 

100.70 

100.00 

2.0000 

Mercuric  Ethide 

(C2HK)2=Hg 

9.97 

143.90 

129.00 

2.1106 

Mercuric  Methide 

(CH3)2=Hg 

8.29 

119.60 

115.00 

2.0607 

Mercuric  Chloride 

Hg  =  Clz 

9.8 

141.50 

135.50 

2.1319 

Mercuric  Bromide 

Hg=Bra 

12.16 

175.60 

180.00 

2.2553 

Mercuric  Iodide 

Hg=Iz 

15.9 

229.60 

227.00 

2.3560 

Mercurous  Chloride 

(Hg2]  =  Cla 

8.21 

118.50 

235.50 

2.3720 

Nitrogen 

N=N 

0.971 

14.00 

14.00 

1.1461 

Ammonia 

H3=N 

0.591 

8.535 

8.51 

0.9294 

Methylamine 

HS,(CH3)=N 

1.08 

15.59 

15.50 

1.1903 

Aniline 

Ha,(C6HB)=N 

3.21 

46.33 

46.50 

1.6675 

Nitrous  Oxide 

NZO 

1.527 

22.04 

22.00 

1.3424 

Nitric  Oxide 

NO 

1.038 

14.97 

15.00 

1.1761 

Nitric  Peroxide 

JVO2 

1.72 

24.82 

23.00 

1.3617 

Osmic  Tetroxide 

OsO4 

8.89 

128.30 

131.60 

2.1193 

Oxygen 

O=O 

1.1056 

15.95 

16.00 

1.2041 

Aqueous  Vapor 

H2=0 

0.6235 

8.998 

9.00 

0.9542 

Phosphorus 

P2!P2 

4.42 

63.78 

62.00 

1.7924 

Phosphuretted  Hydrogen 

Ha=P 

1.184 

17.09 

17.00 

1.2304 

Phosphorous  Chloride 

P=Clg 

4.742 

68.44 

68.75 

1.8373 

Phosphoric  Oxychloride 

P10,  C73 

5.3 

76.49 

76.75 

1.8851 

Oxide  of  Triethylphosphine 

((CaH5)^P)  =  0 

4.6 

66.39 

67.00 

1.8261 

Selenium,  at  771° 

Se=Se 

5.68 

81.96 

79.40 

1.8998 

Seleniuretted  Hydrogen 

Ha=Se 

2.795 

40.33 

40.70 

1.6096 

Silicic  Methide 

(CHs)t=Si 

3.083 

44.49 

44.00 

1.6435 

Silicic  Ethide 

(C2H5)i=Si 

5.13 

74.03 

72.00 

1.8573 

Silicic  Fluoride 

Si  §F4 

3.600 

51.95 

5200 

1.7160 

Silicic  Chloride 

si=a4 

5.939 

85.72 

85.00 

1.9294 

Ethylic  Silicate 

(C2H5),  =  Ot=Si 

7.32 

105.60 

104.00 

1.0170 

Stannic  Ethide 

(C2H5)t=Sn 

8.021 

115.80 

117.00 

2.0682 

Stannic  Dimethylo-diethide 

(CH^^C.H^Sn 

6.838 

98.68 

103.00 

2.0128 

Stannic  Chloro-triethide 

a,(C2Hr,)^Sn 

8.430 

121.70 

120.20 

2.0799 

Stannic  Dichloro-diethide 

C/2,  (  C^H^Sn 

8.710 

125.70 

123.50 

2.0917 

Stannic  Chloride 

Sn  =  Clt 

9.199 

132.70 

130.00 

2.1139 

Sulphur  above  860° 

s=s 

2.23 

32.18 

32.00 

1.5051 

Sulphur  at  450° 

s« 

6.617 

95.50 

96.00 

1.9823 

Sulphuretted  Hydrogen 

H^S 

1.191 

17.19 

17.00 

1.2304 

Sulphurous  Anhydride 

S=03 

2.234 

32.24 

32.00 

1.5051 

Sulphuric  Anhydride 

s=o9 

2.763 

39.87 

40.00 

1.6021 

Tantalic  Chloride 

TaCls 

12.8 

184.70  ' 

179.70 

2.2546 

Titanic  Chloride 

TiClt 

6.836 

98.65 

96.00 

1.9823 

Zinc  Ethide 

(C2fl-5)2=Z» 

4.259 

61.46 

61.60 

1.7896 

Zirconic  Chloride 

Zr=Cl4 

8.15 

117.60 

115.80 

2.0637 

LOGARITHMS  AND  ANTILOGARITHMS. 


LOGARITHMS  OF  NUMBERS. 

-2 

Proportional  Parts, 

•+*  £ 

1 

4 

, 

| 

1 

I 

H 

1  2 

a 

4j5 

67 

8   9  ; 

10 

0000 

0043 

0086 

0128 

0170 

0212 

0253 

0294 

0334 

0374 

4  8 

12 

17 

2 

25  29  33  37 

11 

0414  0453 

0492 

0531 

0569 

0607 

0645 

0682 

0719 

0755 

4  8 

11 

15 

23  26  30  34 

12 

0792  0828 

0864 

0899  0934 

0969 

1004 

1038 

1072 

1106 

3  ~ 

10 

14 

21  24  1  28  31 

13 

1139 

1173 

1206 

1239 

1271 

1303 

1335 

1367 

1399 

1430 

3  6 

10 

13 

19  23  26  29 

14 

1461 

1492 

1523 

1553 

1584 

1614 

1644 

1673 

1703 

1732 

3  6 

9 

12 

18  21 

24 

27 

15 

1761 

1790 

1818 

1847 

1875 

1903 

1931 

1959 

1987 

2014 

3  6 

8 

11 

17  20 

2-2 

25 

16 

2041 

2068 

2095 

2122 

2148 

2175 

2201 

2227 

2253 

2279 

3  5 

8 

11 

16  18  21  24 

17 

2304 

2330 

2355 

2380 

2405 

2430 

2455 

2480 

2504 

2529 

2  5 

7 

10 

15  17  20  22 

18 

2553 

2577 

•2601 

2625  2648 

2672 

2695 

2718 

2742 

2765 

2,  5 

7 

9 

14  16  19 

21 

19 

2788 

2810 

2833 

2856 

2878 

2900 

2923 

2945 

296- 

2989 

\ 

4 

7 

( 

13  16 

18 

20 

20 

3010 

3032 

3054 

3075 

3096 

3118 

3139 

3160 

318 

3201 

S 

t 

6 

8 

13  15 

17 

19 

21 

3222 

3243 

3263 

3284  3304 

3324 

3345 

3365 

3385 

3404 

2  4 

6 

8 

0 

12  14 

16 

18 

22 

3424 

3444 

3464 

3483 

3502 

3522 

3541 

3560 

3579 

3598 

2  4 

6 

8 

o 

12  14 

15 

17 

23 

3617 

3636 

3655 

3674 

3692 

3711 

3729 

3747 

3766 

3784 

2|  4 

C 

' 

9 

11  13 

15 

17 

24 

3802 

3820 

3838 

3856 

3874 

3892 

3909 

3927 

3945 

3962 

2  4 

5 

- 

11!  12 

14 

16 

25 

3979 

3997 

4014 

4031 

4048 

4065 

4082 

4099 

4116 

4133 

2  3 

5 

7 

10  12 

14 

15 

26 

4150 

4166 

4183 

4200 

4216 

4232 

4249 

4265 

428 

4-298 

2  3 

5 

7 

8 

10  11 

13 

15 

27 

4314 

4330 

4346 

4362 

4378 

4393 

4409 

4425 

4440 

4456 

2  3 

5 

6 

8 

9  11 

13 

14 

28 

4472 

4487 

4502 

4518 

4533 

4548 

4564 

4579 

4594 

4609 

2  3 

5 

b 

b 

9,  11  12  14 

29 

4624 

4639 

4654 

4669 

4683 

4698 

4713 

4728 

4742 

4757 

1  3 

4 

6 

' 

9;  10  12 

13 

30 

4771 

4786 

4800 

4814 

4829 

4843 

4857 

4871 

4886 

4900 

| 

4  6 

- 

10  11 

13 

31 

4914 

4928 

4942 

4955 

4969 

4983 

4997 

5011 

5024 

5038 

3 

4  6 

7 

8 

10  11 

12 

32 

5051 

5065  5079  5092 

5105 

5119 

5132  5145 

5159 

5172 

3 

4  5 

7 

8 

9  11 

12 

33 
34 

5185 
5315 

5198 
5328 

9411 

5340 

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5353 

5237 
5366 

5250 
5378 

5263 
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93  IV 

5403 

5289 
5416 

5302 

5428 

3 

4  5 

6 

8 

9  10 

12 
11 

35 

5441 

5453 

5465 

5478 

5490 

5502 

5514 

5527 

5539 

5551 

f 

4  5 

6 

7 

9 

10 

11 

36 

5563 

5575  5587 

5599 

5611 

5623 

5635 

5647 

5658 

5670 

2 

4  5 

6 

7 

8 

10 

11 

37 

568-2 

5694  5705 

5717 

5729 

5740 

5752 

5763 

5775 

5786 

!  c 

3  5 

6 

7 

8 

9 

10 

38 

5798 

5809  5821 

5832 

5843 

5855 

5866 

5877 

5888 

5899 

2 

3  5 

6 

7 

8 

9  10 

39 

Af\ 

5911 

5922 

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5933 

i'A  1  -1 

5944 

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5966 
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5977 

5988 
mnn 

5999 

6010 

2 

3  4 

5 

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8 

9  10 

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41 

6128 

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6138  6149 

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6160  6170 

JUTS 
6180 

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51  17 
6222 

2 

3  4 

5 

6 

7 

8 

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9 

42 

6232 

6243 

6253 

6263 

6274 

6284 

6294 

6304 

6314 

6325 

2 

3  4 

5 

6 

7 

8 

9 

43 

6335 

6345 

6355 

6365 

6375 

6385 

6395  6405 

6415 

6425 

2 

3  4 

5 

G 

7 

8 

9 

44 

6435 

6444 

6454 

6464 

6474 

6484 

6493 

6503 

6513 

6522 

2 

3 

4 

5 

6 

7 

8 

9 

45 

6532 

6542 

6551 

6561 

6571 

6580 

6590 

6599 

6609 

6618 

2 

3 

4 

5 

6 

7 

8 

9 

46 

6628 

6637 

6646 

6656  6665 

6675 

6684  6693 

6702 

671-2 

2 

3;  4 

5 

6 

7 

7 

8 

47 

6721 

6730 

6739 

6749  6758 

6767 

6776  6785 

6794 

6803 

2 

3  4 

5 

5 

6 

7 

8 

48 

6812 

6821  6830 

6839  6848 

6857 

6866  6875 

884 

6893 

a 

3!  4 

4 

5 

6 

7 

8 

49 

6902 

6911 

6920 

6928 

6937 

6946 

6955 

6964 

972 

6981 

2 

3!4 

4 

5 

6 

7 

8 

50 

69906998 

7007 

7016 

7024 

7033 

7042 

7050 

059 

067 

2 

3  3 

4 

5 

6 

7 

8 

51 

7076  7084 

7093 

7101 

7110 

7118 

7126  7135 

143 

152 

2 

3  3 

4 

5 

6 

7 

8 

52 

7160  7168 

7177 

7185 

7193 

7202 

7210  7218 

226 

235 

2 

2  3 

4 

5 

6 

7 

7 

53 

7243 

7251 

7259 

7267 

7275 

7284 

7292  7300 

308 

7316 

2 

2  3 

4 

5 

6 

6 

7 

54 

7324 

7332 

7340 

7348 

7356 

7364 

7372  7380 

388 

7396 

2 

2  3 

4 

5 

6 

6 

7 

LOGARITHMS  OF  NUMBERS. 

1  Natural 
Numbers. 

0 

1 

2 

3 

4 

5 

6 

7 

8 

Propcrt 

onal  Parts. 

9    1234 

567;      9 

55 

7404 

7415 

S7419 

7427 

7435 

7443 

7451 

745 

7466 

7474      1     2     2 

45    56     7 

56 

748-J 

7490  !  7497 

7505  7513 

7520 

7528  753 

754 

7551      1     2     2 

45567 

57 

7559 

7566  7574 

7582  7589 

7597 

7604  761 

761 

7627      122 

45567 

58 

7634 

7642  7649 

7657 

7664 

7672 

7679  768 

769 

7701      1     1     2 

44567 

59 

7709 

7716  7723 

7731 

7738 

7745 

775:2 

776 

776 

7774      1     1    2 

44567 

60  7782  7789  7796  7803  7810 

7818 

7825 

783 

783 

7846      1     1     2 

445           6 

61   7853  7860  7868  7875  '7882 

7889  7896  790 

791 

7917      1     1     2 

4     4566 

62  7924  7931  7938  7945  7952 

7959  7966  797 

798 

7987      1     1     2 

34666 

1    63  '  7S93  8000  8007 

8014  8021 

8028  8035  804 

804 

8055      1     1     2 

34556 

64  8062  8069'  8075 

8082 

8089 

8096 

8102 

8109 

811 

8122      1     1     2 

34666 

65   812981368142 

8149  8156 

8162 

81698176 

818 

8189      1     1     2 

34566 

66  8  195:  8-202  8209,8215  8222 

8228 

8235  8241 

824 

8254       1     1     2 

34566 

67^8261,8267  8274  82808287 

8293 

8299,8306 

831 

8319       1     1     2 

34666 

68  '  832o;8331  8338  8344  8351 

8357 

8363 

8*70 

837 

8382       1     1     2 

34456 

69   8388 

8395  8401  8407  8414 

8420 

8426 

8432 

843 

8445       1     1     2 

34456 

70  8451 

8457  8463 

8470  8476 

8482 

8488 

8494 

8500 

8506       1     1     2 

34456 

71(8513 

8519  8525  8531  8537 

8543 

8549  8555 

856 

8567       Ij    1     2( 

34455 

72  '  8573 

8579  8585  8591  8597 

8603 

8609  8615 

862 

8627       1     1     2 

34465 

73  ;  8633 

86398645 

8651  8657 

8663 

86698675 

868 

8686       1     1     2 

34456 

74*8692 

8698 

8704 

8710 

8716 

8722 

8727  8733 

8739 

8745       li    1     2 

34455 

75  8751 

8756 

8762 

8768 

8774 

8779 

8785 

8791 

879~ 

8802       1     1     2 

33465 

76*8808 

8814 

8820  8825 

8831 

8837 

8842  8848 

8854 

8859       1     1     2 

33465 

77.8865  8871 

8876  8882  8887 

8893 

8899  8904 

8910 

8915       1     1     2 

3-3446 

78^8921  8927 

8932  8938  8943 

8949  8954  8960 

8965 

8971       1     1     2 

33445 

79  8976  8982 

8987 

8993 

8998 

9004 

9009 

9015 

9020 

9025       1122 

33446 

80 

9031  9036 

9042 

9047 

9053 

058 

9063 

9069 

9074 

9079       1122 

33446 

81 

9085  9090 

9096  9101  9106 

9112 

9117 

9122 

9128 

)133      1122 

33446 

82 

913S'9143 

9149  9154  9159 

165 

9170 

9175 

180 

9186       1122 

33446 

83 

9191  9196 

9201  9-206  9212 

217 

9222 

9227 

232 

9238       1122 

33445 

84 

9243  9248 

9253 

9258  9263 

269 

9274 

9279 

284 

289      1122 

33446 

85 

9294  9299 

9304  9309  9315 

320 

9325 

9330 

335 

340      1122 

33446 

86 

9345  9350 

9355  9360  9365 

37Q 

9375 

9380 

385 

390      1122 

33446 

87 

9395^400 

9405  9410  9415 

420  9425 

9430 

435 

440      0112 

93344 

88 

9445  9450 

9455  '  9460  ^465 

469  9474 

9479 

484 

489      0112 

93344 

89 

9494  9499 

9504 

9509  9513 

518 

9523 

9528 

533 

538      0112 

23344 

90 

9542  9547 

9552  9557  9562 

566 

9571 

9576 

581 

586      0           12 

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91 

9590  9595 

9600  9605^609 

9614 

9619 

9624 

628 

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2     3     3     4     4 

92 

96389643 

9647  9652  9657 

661  9666 

9671 

675 

680      0                2 

23344 

93 

9685  9689 

9694  9699  9703 

708  9713 

9717 

722 

727      0               2 

2     3344 

94 

9731 

9736 

9741  9745  9750 

7549759 

9763 

768 

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23344 

95 

9777  9782 

9786  9791  9795 

8009805 

9809 

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23344 

96 

9823  9827 

983298369841 

845  9850 

9854 

859  < 

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23344 

97 

9868  9872  9877  988  l'  9886 

890  9894 

9899 

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2     8j   3    4     4 

98 

9912  9917  99-21  9926  9930 

934  9939  9943 

948  < 

U.v.'     0          1    9 

23344 

99 

9956  9961!  9965  !  9969  9974 

978998319987 

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93334 

ANTILOGARITHMS. 

M 

0 

1 

2 

3 

4 

5 

6 

7 

8 

9 

Proportional  Parts, 

2 

3  4 

a 

A 

0 

1 

8 

9 

.00 

000 

1002 

005 

1007 

009 

012 

014 

016 

019 

021 

0 

0 

1  1 

i 

1 

2 

2 

2 

.01 

023 

1026 

028 

1030 

033 

035 

038 

040 

042 

045 

0 

0 

1  1 

i 

1 

2 

2 

2 

.02 

047 

1050 

1052 

1054 

057 

059 

062 

064 

067 

069 

0 

0 

1  1 

i 

1 

2 

2 

2 

.03 

072 

1074 

1076 

1079 

081 

084 

086 

089 

091 

094 

0 

0 

1  * 

i 

1 

2 

2 

2 

.04 

096 

1099 

1102 

1104 

107 

109 

112 

114 

117 

119 

0 

1 

1  1 

i 

2 

2 

2 

2 

.05 

122 

1125 

1127 

1130 

132 

1135 

138 

140 

143 

146 

0 

1 

1  1 

i 

2 

2 

2 

2 

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148 

1151 

1153 

1156 

159 

161 

164 

167 

169 

172 

0 

1 

1  1 

i 

2 

2 

2 

2 

.07 

175 

1178 

1180 

1183 

186 

1189 

191 

194 

197 

199 

0 

1 

1 

1 

i 

2 

2 

2 

2 

.08 

202 

1205 

120S 

1211 

213 

216 

219 

222 

•225 

227 

0 

1 

1 

1 

i 

2 

2 

2 

3 

.09 

230 

1233 

1236 

1239 

242 

245 

247 

1250 

253 

256 

0 

1 

1 

1 

i 

2 

2 

2 

3 

.10 

259 

1262 

1265 

1268 

271 

1274 

276 

279 

282 

285 

0 

1 

1 

1 

i 

2 

2 

2 

3 

.11 

288 

1291 

1-294 

1297 

300 

1303 

306 

1309 

312 

315 

0 

1 

1 

1 

2 

2 

2 

2 

3 

.12 

318 

1321 

1324 

1327 

330 

334 

337 

1340 

343 

346 

0 

1 

1 

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2 

2 

f\ 

2 

3 

.13 

349 

1352 

1355 

1358 

361 

1365 

368 

1371 

374 

377 

0 

1 

1 

1 

2 

2 

f 

3 

3 

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380 

1384 

1387 

1390 

393 

1396 

400 

1403 

406 

409 

0 

1 

1 

1 

2 

2 

C 

3 

3 

.15 

413 

1416 

1419 

1422 

426 

1429 

432 

1435 

439 

442 

0 

1 

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1 

n 

2 

t 

3 

3 

.16 

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1449 

1452 

1455 

459 

1462 

466 

1469 

472 

1476 

0 

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1 

1 

2 

2 

2 

3 

3 

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479 

1483 

1486 

1489 

493 

1496 

500 

1503 

507 

510 

0 

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2 

r 

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3 

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514 

1517 

1521 

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528 

1531 

535 

1538 

542 

1545 

0 

1 

1 

1 

2 

0 

2 

3 

3 

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549 

1552 

1556 

1560 

563 

1567 

570 

1574 

578 

1581 

0 

1 

1 

1 

<\ 

2 

3 

f 

3 

.20 

585 

1589 

1592 

1596 

600 

1603 

607 

1611 

614 

1618 

0 

1 

1 

1 

0 

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3 

3 

3 

.21 

622 

1626 

1629 

1633 

637 

1641 

644 

1648 

1652 

1656 

0 

1 

1 

2 

B 

2 

3 

3 

3 

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660 

1663 

1667 

1671 

675 

1679 

683 

1687 

1690 

1694 

0 

1 

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2 

2 

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f 

3 

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698 

1702 

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714 

1718 

722 

1726 

1730 

1734 

0 

1 

1 

2 

o 

2 

3 

3 

4 

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1738 

1742 

1746 

1750 

754 

1758 

762 

1766 

1770 

1774 

0 

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1 

2 

t) 

2 

3 

3 

4 

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1778 

1782 

1786 

1791 

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1799 

803 

1807 

1811 

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0 

1 

1 

2 

2 

c 

3 

3 

4 

.26 

1820 

1824 

1828 

1832 

1837 

1841 

1845 

1849 

1854 

1858 

0 

1 

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2 

3 

3 

3 

4 

.27 

1862 

1866 

1871 

1875 

1879 

1884 

1888 

1892 

1897 

1901 

0 

1 

2 

2 

3 

3 

3 

4 

.28 

1905 

1910 

1914 

1919 

1923 

1928 

1932 

1936 

1941 

1945 

0 

1 

2 

2 

3 

3 

4 

4 

.29 

1950 

1954 

1959 

1963 

1968 

1972 

1977 

1982 

1986 

1991 

0 

1 

2 

2 

3 

3 

4 

4 

.30 

1995 

2000 

2004 

2009 

2014 

•2018 

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2028 

2032 

2037 

0 

1 

o 

2 

3 

3 

4 

4 

.31 

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2046 

2051 

2056 

2061 

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2070 

2075 

2080 

2084 

0  1 

1 

o 

2 

3 

3 

: 

4 

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2094 

2099  2104 

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2113 

2118 

2123 

2128 

2133 

0  1 

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2 

2 

3 

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4 

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2138 

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2148  2153 

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2163 

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2173 

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0  1 

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2 

2 

3 

3 

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2234 

1 

2 

2 

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4 

5 

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2239 

2244 

2249 

2254 

2259 

2265 

2270 

2275 

2280 

2286 

1 

2 

2 

3 

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4 

4 

5 

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2291 

2296 

2301  2307 

2312 

2317 

2323 

2328 

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2339 

1 

2 

2 

3 

3 

4 

4 

5 

.37 

2344 

2350 

2356  2360 

2366 

237 

2377 

2382 

2388 

•2393 

1 

2 

2 

3 

3 

4 

4 

5 

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2399 

2404 

2410  2415 

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2427 

243- 

2438 

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2449 

1 

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2 

3 

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4 

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2455 

2460 

2466  2472 

2477 

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2500 

2506 

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2529 

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254 

254 

2553 

255 

2564 

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t 

3 

4 

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2570 

25762582 

2588 

2594 

2600 

260 

261- 

261 

2624 

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2 

i 

3 

4 

4 

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2630 

2636 

2642 

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2655 

266 

2667 

2673 

267 

2685 

1 

fl 

2 

3 

4 

4 

5 

6 

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2692 

2698 

2704 

2710 

2716 

272 

2729 

2735 

274 

2748 

1 

2 

4 

4 

6 

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2754 

2761 

2767 

277 

2780 

278 

2793 

279 

280 

2812 

1 

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3 

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6 

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281£ 

2825 

2831 

2838 

2844 

285 

285£ 

286 

287 

2877 

1 

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5 

6 

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2884 

2891 

2897 

290 

291 

291 

2924 

293 

293 

2944 

1 

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2951 

2956 

296£ 

297 

2979 

298 

2992 

299 

300 

301 

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2 

3 

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6 

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302( 

3027 

3034 

304 

3048 

305 

3062 

306 

307 

308 

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2 

3 

6 

6 

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309( 

)  3097  3105  311 

311 

312 

313S 

314 

314 

315 

] 

2 

5  6 

6 

ANTILOGARITHMS. 

i 

0 

1 

2 

3 

4 

5 

67 

8 

9 

Proportional  Parts. 

r 

2 

3  4*5 

6  7  8 

9 

.50 

3162 

3170  3177 

3184 

3192 

3199 

3206J3214 

3221 

3228 

i 

1 

2  3 

4 

4  5 

6 

7 

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3236  3243  3251  3258  3266 

3273 

328  1!  3289 

3296 

3304 

i 

2 

2l  3 

4 

6 

5 

6 

7 

.52 
.53 

3311  3319  3327  3334  3342 
3388  auofi'a/in/i  -a.iio  QIOO 

335033573365 

3428  ^  A  Qf?  '  Q,4  A  Q 

3373 
3451 

3381 

3459 

1 

2 

2  3 

O  Q 

4 

5 

5 

6 

7 

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3467 

3475  3483 

3491  3499 

3508 

3516,3524 

3532 

3540 

[ 

2 

11 

4 

5 

6 

'  6 

7 

I 

.55 

3548  3556  3565 

3573  3581 

35893597,3606 

3614 

3622 

i 

2 

2 

3 

4 

5 

6 

7 

7 

.56 

3631  3639  3648  3656  3664 

3673 

3681,3690 

3698 

3707 

i 

2 

3  3 

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56 

7 

8 

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3715  3724  3733  3741J3750 

3758 

3767J3776 

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380-2  38  li;3819  ;38-283837 

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2 

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2 

3 

4 

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3981 

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9 

11 

13 

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7980 

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8017 

8035 

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.91 

8128 

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8241  '  8260 

8279 

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9 

11 

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17 

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8318 

8337 

8356  8375 

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8414  8433  '  8453 

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4 

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10 

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15 

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10 

1-2 

14 

16 

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8730 

8750 

8770 

8790 

8810 

8831J8851 

8872 

8892 

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4 

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14 

16 

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8913 

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8974 

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9016 

9036  9057 

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4 

6 

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17 

19 

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9120!9141 

9162 

9183 

9204 

9226 

9247  9268 

9290 

9311 

2 

4 

6 

1 

11 

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15 

17 

19 

.97 

9333  9354 

9376  9397 

9419 

9441 

9462  9484 

9506 

9528 

2 

4 

7 

9 

11 

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U 

17 

20 

.98 

9550,9572 

9594 

9616  9638 

9661 

9683  9705 

9727 

9750 

2 

4 

7 

9 

11 

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16 

18 

20 

.99 

9772  9795 

9817 

98409863 

9886 

9908  !  9931 

9954 

9977 

2 

5 

7 

9 

11 

14 

16 

18 

20 

CONSTANT    LOGAKITHMS. 

Loga-  Ar.  Co. 

rithms.  Log. 

Circumf.  of  circle  when  R  =  1,  (^  =  1.5708)  0.1961  9.8039 

"  "  «  "  D  =  1,  (TI  =  3.1416)  0.4971  9.5028 

Area  of  circle  when  2?=  1,  (n  =  3.1416)  0.4971  9.5028 

"  "  "  "  ZP=1,  (~  =  0.7854)  9.8951  0.1049 

"  «  «  «  C"=l,  Q^  =  0.0796)  8.9008  1.0992 

Surface  of  sphere  when  #2=  1,  (4^=12.5664)  1.0992  8.9008 

«  "  "  "  jDa=l,  (TT  =  3.1416)  0.4971  9.5028 

«  «  "  «  C2=l,  (^  =  0.3183)  9.5028  0.4971 

Solidity  of  sphere  when  223=  1,  (|^=  4.1888)  0.6221  9.3779 

«  "  «  "  D8=l,  (^  =  0.5236)  9.7190  0.2810 

«  "  "  "  C»=l,  (g^a=  0.0169)  8.2275  1.7724 

Weight  of  one  litre  of  Hydrogen  (0.0896  grammes)  8.9522  1.0478 

«       "     "      4<     «  Air             (1.293           "       )  0.1116  9.8884 

"       ".    "      "      "    "               (14.43     criths     )  1.1594  8.8406 

Per  cent  of  Oxygen  in  air  by  weight    (0.2318)        9.3651  0.6349 

"       «     "Nitrogen"   "    "       "          (0.7682)        9.8855  0.1145 

Mean  height  of  Barometer                    (76  c.  m.)        1 .8808  8. 1 1 92 

Coefficient  of  expansion  of  Air            (0.00366)        7.5635  2.4365 

Latent  Heat  of  Water                                   (79)        1.8976  8.1024 

«         «      «  Free  Steam                        (537)        2.7300  7.2700 

To  reduce  0p.(^r. to  SP-  Gr.,  or  reverse,  add  to  log.  1.1594  or  8.8406 

"        "      Sp.  Gr.    toSp.Gr.,"       "          "    "   "      5.9522  or  4.0478 

"        "      0p.(^r.  to  Sp.  Gr.,  "        "          "    "   "      7.1 116  or  2.8884 

<*        «      grammes  to  criths,  ««       "         "    "  "      1.0478  or  8.9522 


INDEX. 


The  numbers  of  this  Index  refer  to  pages ;  those  following  dashes  are  references  to 
reactions,  into  which  the  given  substance  enters  as  an  important  factor.  To  use  the 
index  with  copies  of  the  first  edition,  add  ten  to  the  number  of  all  pages  above  the  two 
hundredth. 


A. 


Acetamide,  243.— 245. 

Acetic  Acid,  74,  488,  493.  —513. 

"      Anhydride,  493. 

«      Ether,  492.  -  61,  490. 
Acetine,  517- 
Ace  to-lactic  Acid,  510. 
Acetone,  495. 
Acetonyl,  484. 
Acetyl,  73,  484. 

"      Chloride,  —  57,  496. 
Acetylene  Series,  477,  480. 
Acidity  of  Bases,  94. 
Acids,  Definition  of,  83. 
Acid  Radical?,  83. 

"     Salts,  87. 
Aconitic  Acid,  518. 
Acrolein,498. 
Acryl,  484. 
Acrylic  Acid,  498. 

"        Series,  498. 

"         "       Secondary  Acids,  499. 

"          "       Tertiary  Acids,  500. 
Adhesion,  12,  37. 
Adipic  Acid,  512. 
Agalmatolite,  410. 
Agate,  445 
Alabaster,  342. 
All  bite,  409. 
Albumen,  524. 

Alcohol,  90,  485,  487.  —  38.  77,  358,  455, 
491,  492,  509,  512. 

"        Digly eerie,  517. 
Iso,  496. 

"        Pseudo, 486,  496. 

"        Radicals,  73 

"        Secondary,  496. 

"        Tertiary,  497. 

"        Tetratomic,  519. 

"        Triatomic,  515. 

"        Trigly eerie,  517. 
Aldehyde,  487,  494.  —  509. 
Alkali,  Definition  of,  81. 

"      Fixed,  247. 

"      Volatile,  247. 
Alkaline  Sulphides,  312. 

"        Sulphohydrates,  312. 
Allotropisra,  133.  —  251,  302,  308,  460. 
Allyl,  78,  477,  481. 
Allylic  Alcohol,  497. 

"      Iodide, —481,497. 

"      Cyanide, —500. 
Allylene,  477. 
Altaite,  321. 

Alums,  319,  376,  400,  409,  412. 
Aluminates,  414. 
Aluminic  Acetate,  413. 

Chloride,  414,  415. 


Aluminic  Hydrate,  408,  414. 
Nitrate,  414. 

"        Oxide,  415. 

"        Sulphate,  409,  413.  414. 

"        Sulphide,  415. 
Aluminite,  409. 
Aluminum,  408.  — 412. 

"          Bronze,  411. 
Alum-stone,  409. 
Alunite,  409. 
Alunogen,  409. 
Amethyst,  445. 
Amides,  243. 
Amidogen,  39,  243. 
Amines,  242. 

Ammonia,  82, 240. —36, 38,82,233,246,494. 
Ammonic  Carbonates,  248.  —  246,  341. 

"         Chloride,  247.  —  38,  241. 

"         Dichromate,  —  399. 

"         Nitrate,  —  239. 

"        Nitrite, —233. 

"         Silico-fluoride,  452. 
•    "         Sulphohydrate,  312. 

"         Sulphide,  311,  312.  —  361. 
Ammonides,  242. 
Ammonio-cobalt  Bases,  369. 
Ammonio-magnesic  Phosphate,  356. 
Ammonio-manganous  Salts,  374. 
Atnmonio-platinous  Chloride.  427. 
Ammonio-platinic  Chloride.  426. 
Ammonio-platinum  Bases,  428. 
Ammonio-stannic  Chloride,  435. 
Ammonium,  82,  246. 

Alum,  409.  413. 
"          Bases,  248. 
"          Compounds,  245. 
Ampere's  Law,  17. 
Amygdaline,  522. 
Amylaceous  Bodies,  521. 
Amylene,  477. 
Amyl,  72,  484. 
Amy  lie  Alcohol,  486. 
"       Acetate,  492. 
14      Glycerine,  f>18. 
"      Hydride,  477. 
'«       Acid  Sulphate,  —  492; 
Amyloses,  521. 
Analcime,  410,  456,  457. 
Analysis,  9. 

Analytical  Reaction,  35 
Anchoic  Acid,  512. 
Andalusite.  409.- 
Andesine,  457. 
Angelic  Acid,  498. 
Anglesite,  346. 
Anhydrides  Acid,  85 

"          Basic,  82. 

"          of  Organic  Acids,  493. 
Anhydrite,  342. 


INDEX. 


Aniline,  242,  482.  —  502. 

Animal  Kingdom,  Province  of,  525. 

Ankerite,  378. 

Annabergite,  365. 

Anorthite,  409,  456. 

Antimoniate  of  Antimony,  270. 

Antimonic  Acid,  269. 

"         Anhydride,  270. 
"         Chloride,  267. 
"         Sulphochloride,  267. 
"         Sulphide,  275. 
Antimonious  Bromide,  267. 

Chloride,  266.— 268,270. 
"  Fluoride,  267. 

"  Hydrate,— 61. 

"  Iodide,  267. 

H  Oxide,  267.  —  264. 

*'  Sulphate, —265. 

"  Sulphide,272.-264,266,310. 

Antimoniuretted  Hydrogen,  270. 
Antimony,  264.  —  265,  266. 
"        Butter  of,  266. 
"        and  Alcohol  Radicals,  27L 
"          "    Chlorine,  266. 

"    Hydrogen,  270. 
"          "    Oxygen,  267. 
"          "    Sulphur,  272. 
"          «*    Zinc,27i. 
"        Glance,  264,  272. 
"        Oxychloride  of,  266. 
Antozone,  304. 
Antozonides,  305. 
Apatite,  291,  343. 
Apjohnite,  409. 
Aqua  Ammonia,  247. 

"    Regia,224. 
Arachidic  Acid,  488. 
Aragonite,  340. 
Argentic  Bromide,  221. 
"       Chloride,  221. 
"       Iodide,  221. 

"       Nitrate,  220.  -  36,  38,  56,  236. 
[     "       Oxalate,  —  465. 
'     "       Oxide,  222.  —  249. 
"       Peroxide,  222. 
"        Sulphate,— 54. 
"       Sulphite,  —  315. 
Arsenic,  257. 
"      Acid,  259. 

"      and  Alcohol  Radicals,  261. 
"        "    Chlorine,  263. 
"        "    Hydrogen,  260. 
"        "    Iodine,  263. 
"        "    Sulphur,  263. 
"      Anhydride,  260. 
"      Compounds  with  Bromine,  263. 
Arsines,  261. 
Arsenide  of  Tin,  —260. 
Arsenious  Anhydride,  258.  —  257. 
"        Bromide  and  Iodide ,  263. 

Sulphide,  263. 
Arsenites,  259. 

Arseniuretted  Hydrogen,  260. 
Artiad  Elements,  300. 
Artiads,  Definition  of,  59. 
Atacamite,  331. 
Atmosphere,  114. 
Atomicity,  55. 

"         of  Acids,  93. 
11         of  Radicals,  59. 
Atomic  Ratio,  448. 
"     Weight,  25,  28. 


Atomic  Weights,  Relations  of,  195. 
Atoms,  Definition  of,  24. 

"      Negative,  168. 

"      Positive,  168. 

Quantivalence  of,  59, 132. 

"      True  Idea  of,  70. 
Atom-fixing  Power.  57. 
Augite,  356. 
Auric  Salts,  224. 
Auriferous  Quartz,  222. 
Aurous  Salts,  224. 
Axinite,  228. 
Azurite,  330. 


Baric  Chloride,  344.  —  36. 
'     Hydrate,  345.  —  82. 

Nitrate,  344. 

Oxide,  345.  —  35. 

Peroxide,  345.  —  203. 

Sulphide, —345. 
Bario-platinic  Chloride,  426. 
Bario-stannous  Chloride,  435. 
Barium,  344. 
Bases,  Definition  of,  80. 
Basic  Ferric  Hydrates,  386. 
"     Radicals,  83. 
"     Salts,  87. 

Basicity  of  Acids,  93,  465. 
Beauxite,  408. 
Behenic  Acid,  488. 
Benzamide,  76,  243. 
Benzine,  482. 

Benzoic  Acid,  501,  503.  —  482. 
"       Alcohol,  601. 
"       Ether,  493. 
Benzoin  Gum,  603. 
Benzol,  477,  482.  —  235. 
Benzoyl,  503. 
Berthierite,  273. 
Beryl,  363,  456. 
Berzelianite,  320. 


Bismuth,  275. 

and  Alcohol  Radicals,  276. 
Basic  Nitrate,  278. 
Compounds  with  Oxygen,  277. 

"  "    Sulphur,  278. 

Glance,  275. 
Magistery  of,  278. 
Oxychloride  of  276. 
Bismuthic  Compounds,  277. 
Bismuthous  Compounds,  276,  277,  278. 
Black  Ball,  214. 
Blast  Furnace,  380. 
Bleaching,  207,  314. 

"          Powder,  341. 
Blende,  357. 
Bloom,  380. 
Bloomery  Forge,  380. 
Blue  Pill,  333. 
Blue  Vitriol.  329. 
Bog  Ore,  378. 
Bone  Black,  458. 
Boracite,  232. 
Borax,  230.  —  229. 
Boric  Acid,  229.  —  86. 
"    Anhydride,  86,  229.  —  228,  231. 
"     Bromide,  231. 
"     Chloride,  231. 
"     Fluoride,  231.      , 


INDEX. 


Boric  Sulphide,  232. 
Borofluoric  Acid,  231. 
Boron,  228. 
Botryogen,  379. 
Bournonite,  273. 
Brackets,  Use  of,  74. 
Braunite,  373. 
Breithanphite,  365. 
Bricks,  411. 
Britannia  Metal,  266. 
Brochantite,  330. 
Bromhydrine,  505. 
Bromine,  210.  —  499,  504. 
Bromoform,  494 
Brookite,  430. 

Brown  Clay  Iron  Stone,  378. 
Brown  Hematite,  378. 
Brucite,  354. 
Brunswick  Green,  331. 
Bunsenite,  365. 
Bunsen's  Cell,  164. 
Burning,  114. 
Butyl,  4$4. 
Butylic  Alcohol,  485. 

"       Glycol,  505. 

"       Hydride,  477. 
Butylene,  477. 
Butyric  Acid,  488. 

"       Anhydride,  493. 

"       Ether,  492. 

"      Butyryl,  484. 


0. 

Cacoxenite,  379. 
Cadmio-Zirconic  Fluoride,  440. 
Cadmium,  359. 
Caesium,  217. 
Calamine,  357. 
Calcareous  Marl,  340. 
Calcic  Acetate,  —  495. 

Carbonate,  340.— 344. 

Chloride,  343. 

Chromate,  403. 

Fluoride,  343.  —  207,  452. 

Hydrate,  341.  —  82,  96,  313. 

Hyposulphite,  315. 

Nitrate,  344. 

Oxalate,  —  464. 

Oxide,  341. 

Peroxide,  342. 

Persulphide,  313. 

Phosphate,  343.  — 250. 

Silicate,  343- 

Sulphate,  342. —313. 

Sulphide,  313. 

Sulphite,  315. 
Calcined  Magnesia,  354. 
Calcite,  340. 
Calcium,  340. 
Calomel,  334. 
Calorific  Intensity,  119. 

"        Power,  118,  122. 
Cane  Sugar,  521. 
Capric  Acid,  488. 
Caproic  Acid,  488. 
Caprylic  Acid,  488. 
Carbolic  Acid,  502. 
Carbon  458.  — 115,467. 
Carbonic  Acid,  462. 

"        Anhydride,  461.  —  465. 


Carbonic  Chloride  —478. 

"        Oxide,  462.— 463. 

44        Sulphide,  466.  — 478. 
CarbonyL,  39,  463,  484. 
Carnallite,  216. 
Carnelian,  445. 
Carre's  Apparatus,  24L 
Cassiterite,  433. 
Caustic  Potash,  216. 

"      Soda,  214. 
Celestine,  344. 
Cementation,  382. 
Cerite,  364. 
Cerium,  364. 
Cerotene,  477. 
Cerotic  Acid,  488. 

"      Alcohol,  485. 
Cerusite,  346. 
Cervantite,  270. 
Cetene,  477. 
Cetylic  Alcohol,  486. 
Chabaiite,  410. 
Chateostibite,  273. ' 
Chalcotrichite,  329. 
Chalcedony,  445. 
Chalk,  340. 

Chameleon  Mineral,  377. 
Charcoal,  458. 

"        Animal,  458. 

Chemical  Change,  Characteristics  of;  3, 110- 
Chemistry,  Definition  of,  3 
Chili  Saltpetre,  215. 
Chinese  Wax,  488. 
Chiolite,  408. 
Chloanthite,  365. 
Chloracatic  Acid,  67. 
Chlorhydrines,  402,  504,  516. 
Chloric  Acid,  209. 

"      Peroxide,  209. 

Chlorine,  207.  -  208, 231, 233, 341, 399, 452, 
471,  493. 

"        Compounds  with  Oxygen,  209. 
Chlorite,  356,  410. 

Chlorochromic  Anhydride,  404.  —399. 
Chloroform,  494.  —  38,  57. 
Chlorous  Acid,  209. 

44        Anhydride,  209. 
Choke  Damp,  461. 
Chromates,  402. 
Chromatic  Spectra,  176. 
Chrome  Alum,  400. 

"       Green.  399,  404. 

"       Iron,  398. 

"       Orange,  403- 

"       Yellow,  403 
Chromic  Anhydride,  404. 

44       Chlorhydrines,  402. 

41       Chloride,  401. 

"       Fluoride,  405 

"       Hydrates,  400,  82. 

"       Nitrate,  401. 

"       Oxalates,  401. 

14       Oxides,  399. 

14       Sulphates,  400. 

"       Sulphides,  405. 
Chromite,  398. 
Chromium,  398. 
Chromous  Chloride,  398. 

44         Hydrate,  399. 
Chrysoberyl,  363,  408. 
Chrysolite,  356. 
Cinnabar,  332. 


IV 


INDEX. 


Cinnamene,  483. 
Cinnamic  Acid,  503. 
Citraconic  Acid,  514. 
Citric  Acid,  519. 
Classification,  Grounds  of,  192. 
"  Scheme  of,  193. 

Clay  Iron  Stone,  378. 
Clays,  410. 
Cleavage,  152. 

"        Eminent,  152. 
Coal,  458. 
Cobalt,  367. 

"       Ammonio-Bases,  369. 
"       and  Oxygen,  368. 
"       Bloom,  368. 
"       Vitriol,  368. 
Cobalticyanides,  370. 
Cobaltine,  368. 
Coefficient  of  Expansion,  14. 

"          M  Absorption,  109. 
Cohesion,  12.  —  37. 
Coke,  459. 
Colcothar,  388. 
Colloids,  111. 
Color,  175. 
Columbite,  296. 
Columbium,  296. 

"  Compounds  of,  296,  297. 

Combustion,  114. 

"  Heat  of,  117. 

Common  Salt,  213 
Compound,  Definition  of,  7,  10. 

Radicals,  38,  83. 

Compounds,  Classes  of,  62,  80, 101. 
Conine,  249. 
Copiapite,  379. 
Copper,  328. 

"       Ammouiated  Compounds,  331. 
"      Compounds  with  Oxygen,  329. 
"      Fluohydrate,  331. 
"      Glance,  330. 
"     Pyrites.  328,  330. 
"      Salts,  329. 
Coquimbite,  379. 
Corrosive  Sublimate,  335. 
Corundum,  408. 
Covelline,  330. 

Cream  of  Tartar,  217.  —214,  268. 
Creosote,  502. 
Cresylic  Alcohol,  503. 
Crith,  2. 
Crocoite,  398. 
Crocus  Martis,  388. 
Crotonic  Acid,  498. 
Crotonylene,  477. 
Cryolite,  207,  408. 
Crystalline  Axes,  138. 
"  Form,  138. 

"  "      Identity  of,  146. 

«          Structure,  152. 
Symmetry,  137. 
"  Systems,  138. 

Crystalloids,  111. 
Crystals,  Irregularities  of,  148. 
"       Modifications  on,  143. 
"        Twin,  150. 
Cumin,  Essential  Oil  of,  501. 
Cuminic  Acid,  501,  503. 
"        Aldehyde,  501. 
Cumol,  477. 
Cumylic  Alcohol,  501. 
Cupellation,  220. 


Cupric  Carbonates,  330. 
"      Chlorides,  331. 
Hydride,  331. 
Nitrates,  330. 
Oxide,  329.  —  84. 
Oxychloride,  331. 
Phosphate,  330. 
Silicate,  330. 
Silico-fluoride,  452. 
Sulphate,  329.  —  54. 
Sulphides,  330. 
Cuprous  Chloride,  331. 
Current,  Electric,  Negative,  157. 
4  "          Positive,  157. 

1  "          Strength  of,  160. 

'  "         Unit  of,  169. 

Cyanates,  472. 
Cyanetholine,  473.  —  77. 
Cyanhydrine,  505. 
Cyanic  Acid,  471.  —  77- 

"      Ethers,  472.  —  77. 
Cyanides,  468. 
Cyanite,  409. 
Cyanogen,  466. 

"          Compounds  with  Chlorine,  471 
Cyanuric  Acid,  471. 
Cymol,  477. 


D. 


Danburite,  228. 

Dark  Red  Silver  Ore,  220. 

Datholite,  228. 

Definite  Proportions,  Law  of,  9. 

Dextrose,  522. 

Dialysis,  112. 

Diammonic-ferric  Sulphate,  386. 

Diamond,  459. 

Diaspore,  408. 

Diatomic  Acids.  93,  507 

Dibasic  Acids,  93,  268,  512. 

Dibromhydrine,  505. 

Dichlorhydrine,  516. 

Dicyanic  Acid,  471. 

Didymium,  364. 

Diethoxalic  Acid,  511. 

Diffusion  Gaseous,  112. 

"        Liquid,  110. 
Dimethoxalic  Acid,  511. 
Dimetric  System,  139. 
Dimorphism,  135,  252,  335. 
Dinitro-benzol,  482. 
Dioptase,  330. 
Diplumbic  Chromate,  403- 
Disassociation,  128,  325  Prob.  38,  339  Prob. 

30. 

Disinfectants,  207,  314. 
Dolomite,  355. 
Drummond  Light,  341. 
Dufrenite,  379. 
Dufrenoysite,  263. 
Dutch  Oil,  479. 


Earthen  Ware,  411. 
Earthy  Cobalt,  368. 
Electrical  Conducting  Power,  157. 

"  Resistance,  157, 169. 
Electric  Current,  156, 160,  169. 
Electricity,  155. 

"         Intensity  of,  161. 


INDEX. 


Electricity,  Quantity  of,  161. 
Electrolysis,  165. 

Electromotive  Force,  159, 160, 169. 
"  "        Unit  of,  169. 

Electroplating,  167,  221. 
Elements,  7 

"         Classes  of,  192. 
"         Distribution  of,  8. 
"         Individuality  of,  70, 190. 
Emerald  Nickel,  365. 
Emery,  408. 
Emplectite,  279. 
Enargite,  263. 
Epidote,  410,  456. 
Epsom  Salts,  355. 
Equivalency,  Chemical,  54. 
Equivalents,  54. 
Erbium,  363. 
Erubescite,  330. 
Erythrite,  368,  519. 
Etheric  Acids,  508. 

"       Secondary,  510. 
Etherification,  491. 
Ethers,  90,  491.  —  492. 
"       Compound,  492. 
"       Haloid,  493. 
u       of  Glycerine,  517. 
"       Mixed,  492. 
Ethomethoxalic  Acid,  511. 
Ethyl,  484. 

Ethylamine,  58,  242,  245,  472. 
Ethyl-glycollic  Acid,  511. 
Ethyl-lactic  Acid,  510. 
E  thy  lie  Acetate,  —  491. 
"       Alcohol,  485. 
Chloride,  —  492. 
Cyanide,  —  489. 
Glycol,  505. 
Hydride,  477. 
Iodide,  —  479,  494. 
Sulphate,  —  491. 
Ethylene,  477.  —  479,  480,  504,  508. 

Bromide,  479.  —  61,  480,  506. 
"         Bromhydrine,  505.  —  506,  507. 
"         Chloride,  479. 

Cyanhydrine,  505-  -  609. 
«'         Ether,  505. 
"         Glycols,  506. 
"         Iodide,  479. 
"         Oxide,  505. 
Ethylidene  Chloride,  509. 

"         Cyanhydrine,  510. 
Ethyline,  517. 
Essential  Oil  of  Cumin,  501. 

Oils,  477,  481. 
Eudialyte,  439. 
Euxenite,  296,  441. 
Exchanges,  Theory  of,  189. 
Expansion  by  Heat,  14. 

P. 

Fat  Acids,  90,  487. 
"      "       Isomers  of,  49L 
Fats,  518. 
Fayalite,  379. 
Feldspars,  409. 
Fergusonite,  296. 
Fermentation,  523. 
Ferrates,  389 
Ferric  Acetate,  3S6. 
"     Arseniates,  379. 


Ferric  Chloride,  386,  387.  ~  470. 
'     Ferrocyanide,  470. 
Hydrates,  378\  386. 
Nitrate,  386. 
Oxalate,  386. 
Oxide,  378, 388.  — 469. 
Silicates,  379. 
Sulphate,  379,  386. 
Sulphides,  378,  388. 
Ferricyanides,  470. 
Ferrocyanides,  469. 
Ferrous  Carbonate.  378,  384. 

"       Chloride,  385,  387.  —  235,  470. 
"       Ferric  Oxide,  378,  388. 
"       Hydrate,  385,  82. 
"       Nitrate,  385. 
'*      Oxalate,  385. 
"       Oxide,  388. 
"        Phosphate.  385. 
"       Sulphate,  385. —226. 
"  "         JMpotassic,  393. 

"       Sulphide,  388.  —  309,  469. 
Fibroferrite,  379. 
Fire  Damp,  478. 
Flint,  445. 
Float  Stone,  445. 
Fluorine,  207. 
Fluor  Spar,  343, 207. 
Formic  Acid,  488,  490.  —  464, 514. 
Formyl,  484. 
Forsterite,  457. 
Fowler's  Solution,  259. 
Franklinite,  378. 
Freieslebenite,  273. 
Fumaric  Acid,  514. 
"       Series,  514. 
Fusible  Alloy,  276. 

G. 

Gadolinite,  363, 441. 

Gahnite,  408. 

Galena,  346. 

Gallic  Acid,  623. 

Galvanic  Battery,  161. 

Garnet,  410,  448,  457. 

Gaseous  State,  12. 

Gases,  Molecular  Condition  of,  17. 

Gas,  Illuminating,  478. 

Gay  Lussac's  Law,  48. 

Genthite,  365. 

German  Silver,  366. 

Gibbsite,  408. 

Gilding,  226. 

Glass,  214,  216,  447. 

Glaucodot,  368. 

Glockerite,  379. 

Glucinnm,  363. 

Glucose,  521.  — 524. 

Glucoside,  522. 

Glyoeric  Acid,  516. 

Glycerides,  518. 

Glycerine,  93,  515.  —  497.  498,  518. 

Chlorhydrines,  516. 

Ethers  of,  617. 
Glyceryl,  484,  616. 

"        Bromide,  —  618. 
Chloride,  —  61. 
Chlorhydrine,  516.  —  617. 
"        Cyanide.  —  618. 
Glycide,  517. 
Glycocoll,  244,  77. 


INDEX. 


Glycol,  92,  504. 

"      Condensed,  506. 
"      Sulphur,  505. 
Glycollic  Acid,  92,  505,  508,  509. 
Glycolyl,  484. 
Glyoxal,  511.  -  512. 
Glyoxalic  Acid.  611.  —  512. 
Gold,  222. 

"     Bromide,  225. 

"     Chloride,  224.  —  226. 

"     Iodides,  225. 

"     Oxides,  225. 

"     and  Sodium  Hyposulphite,  225. 

"     Sulphides,  225. 
Gbthite,  378. 
Granites,  411. 
Graphite,  459. 
Graphitic  Acid,  459. 
Gray  Iron,  381. 
Greenockite,  359. 
Green  Stone,  411. 

"     Vitriol,  379, 384. 
Grove's  Cell,  163. 
Guano,  34a 
Gum,  521. 

Gun  Cotton,  66,  522. 
Gunpowder,  216. 
Gypsum,  308, 342. 

H. 

Halloysite,  410. 
Halotrichite,  409. 
Hard  Water,  340. 
Harmotome,  410,  456- 
Hauerite,  373. 
Hausmannite,  373. 
Heat,  13. 

1      of  Chemical  Combination,  123. 
1      of  Combustion,  117. 

"      Expansion  by,  14. 

"      Latent,  16. 

*      Sources  of,  16. 

"     Specific,  16. 

"     Unit  of,  14. 
Heavy  Spar,  344. 
Hematite,  378. 
Hemihedral  Forms,  145. 
Hemitropes,  150. 
Hercynite,  408. 
Hessite,  321. 
Heulandite,  410,  457. 
Hexagonal  System,  140. 
Hexatomic  Organic  Compounds,  620. 
Hexylene  lode-hydride ,  521.      ' 
Hippuric  Acid,  244,  77. 
Holohedral  Forms,  146. 
Homologous  Series,  475. 
Homologues,  475. 
Honey,  522. 
Hornblende,  356. 
Horn  Silver,  220. 

"     Stone,  445. 
Hydrates,  80,  230,  445. 
Hydric  Oxide,  201. 

Peroxide,  202. 
Persulphide,  312. 
Selenide,  320. 

Sulphide,  309.  —  310,  311,  387. 
Tefluride,  320. 

Hydriodic  Acid,  210.  —  84,  516,  520. 
Hydrobromic  Acid,  210.  —  84. 


Hydrocarbon  Radicals,  483. 

Hydrocarbons,  474. 

Hydrochloric  Acid,  208.  —  84,  207, 


Hydrocyanic  Acid,  468.  -  40,  371,  469, 489. 
Hydrofluoboric  Acid,  232. 
Hydrofluoric  Acid,  207. 
Hydrogen,  201.  -  202,  260,  478,  499. 

Alcoholic  Atoms,  94,  244,  465. 
"         Basic  Atoms,  94,  244,  465. 
Hydrogenium,  425. 
Hydromagnesite,  355. 
Hydro-silicic  Fluoride,  452. 
Hydro-titanic  Fluoride,  431. 
Hydroxyl  and  its  Analogues,  202,  302, 
Hypochlorous  Acid,  209.  —  504. 
Hypochlorous  Anhydride,  209. 
Hypophosphorous  Acid,  252,  255. 
Hyposulphites,  315. 
Hyposulphurous  Acid,  313,  315. 


Ignition,  Point  of,  122. 

Ilvaite,  379,  457. 

Imides,  245. 

Indelible  Ink,  221. 

Indigo  Copper,  330. 

Indium,  359. 

Ink,  523. 

lodic  Acid,  —  314. 

Iodine,  210.  —  493. 

lodoform,  494. 

lolite,  456. 

Indium,  422. 

Iridium  Compounds,  422. 

Iridosmine,  418. 

Iron,  377.  —39. 

Cast,  380. 

Metallurgy  of,  879. 

Olivine,  379. 

Passive  Condition  of,  384. 

Pyrites,  308,  378. 

Wrought,  380. 
Iso-acids,  491,  507. 
Isoamylic  Alcohol,  497. 
Isohexylic  Alcohol,  497. 
Isohexylic  Iodide,  521. 
Isologne,  475. 
Isomaleic  Acid,  514. 
Isomerism,  133. 

"         in  Lactic  Family,  511. 
Isometric  System,  138. 
Isomorphism,  68. 

Isomorphous  Mixtures  Notation  for,  274. 
Isopropylic  Alcohol,  496. 
Itaconic  Acid,  514. 
Ivory,  Black,  458. 


J. 


Jamesonite.  273. 
Jarosite,  379. 
Jasper,  445. 


Kakodyl,  261. 
Kaolinite,  410. 
Ketones,  495. 
Kieserite,  356. 
Kobellite,  279. 
Kupfernickel,  365, 


INDEX. 


vii 


Labradorite,  409. 

Lactaniide,  244,  245. 

Lactic  Acid,  94,  509,  611.  —  524. 

Lactic  Family,  507. 

"          "        Isomerism  in,  511. 

"          "        Normal  Acids,  508. 

"          "        Secondary  Acids,  509. 

"          "        Tertiary  Acids,  511. 
Lactimide,  245. 
Lac tme thane,  244. 
Lactyl,  484. 
Lakes,  412. 
Lamp  Black,  458. 
Lanthanite,  364. 
Lanthanum,  364. 
Lapis  Lazuli,  410. 
Laughing  Gas,  239. 
Laurie  Acid,  488. 
Lava,  411. 
Law  of  Ampere,  17. 

"     Definite  Proportions,  9. 

"     Gay  Lassac.  48. 

'•     Mariotte,  12. 

"     Multiple  Proportions,  10. 

41     Ohm,  159. 
Lazulite,  409. 
Lead,  346. 

"     Soap,  515. 
Leucic  Acid,  509. 
Leucite,  409,  456. 
Leukon,  454. 
Levulose,  522. 
Light,  174. 

Light  Red  Silver  Ore,  220. 
Lime,  341.  —  81,  482. 

"      Chloride  of,  341. 
Limestone,  340.' 
Lime  Water,  341. 
Lininite,  378. 
Limonite,  378. 
Linnaeite,  368. 
Liquation,  272. 
Liquid  State,  12. 
Litharge,  347. 
Lithium,  217. 
Loadstone,  383. 
Lunar  Caustic,  220. 

M. 

Magnesia  Alba,  355. 
Magnesic  Carbonate,  355 

"        Chloride,  356.  —  361. 

"        Hydrate,  354.  —  81. 

"        Oxide,  354. 

«        Silicates,  356. 

"        Sulphate,  355. 
Magnesioferrite,  378. 
Magnesite,  355. 
Magnesium,  354.  —  61. 
Magnetic  Pyrites,  378. 
Magnetite,  378. 
Malachite,  330. 
Malacone,  441. 
M.ileic  Acid,  514. 
Malic  Acid,  515,  520. 
Malonic  Acid,  505,  512. 
Malonyl,  484. 
Manganblende,  373. 
Manganese,  373. 


Manganese,  Brown ,  374 

"          Red,  Oxide  of,  374. 
"          Spar,  373. 
Manganic  Chloride,  375. 

Dioxide,  375.  —  207,  300. 
"         Hydrate,  375. 
Manganite,  373. 
Manganocalcite,  373. 
Manganous  Compounds,  374. 

"          Silico-fluoride,  452. 
Manna,  520. 
Mannite,  520. 
Mannitic  Acid,  520. 
Marble,  340. 
Marcasite,  378. 
Margaric  Acid,  488. 
Mariotte's  Law,  12. 
Marsh  Gas,  478.  —  486. 

"      "     Series,  477,  478. 
Massicot,  346. 
Melaconite,329. 
Melene,  477. 
Melissic  Acid,  488. 

"       Alcohol,  486. 
Menaccanite,  378. 
Meneghinite  27& 
Mercaptan,  487. 
Mercuramine,  336. 
Mercuric  Chloride,  335 
Cyanides.  467. 
Iodide,  335 
Nitrate,  333.  —  334. 
Oxide,  333. 
Sulphate,  334. 
Sulphide.  334.  —  332. 
Mercurous  Chloride,  334. 

Chromate.  —  399. 
Nitrate,  333. 
Oxide,  333. 
Sulphate,  333. 
«         Sulphide,  334. 
Mercury,  332. 

"        Ammoniated  Compounds,  335. 
Mesaconic  Acid,  514. 
Mesitite,378. 

Metaphosphoric  Acid,  253. 
Metastannic  Hydrate,  436. 
Metathesis,  Conditions  of,  37. 
Metathetical  Reaction,  36. 
Methyl,  72,  484. 
Methylamine,  242. 
Methyl-gly collie  Acid,  510. 
Methyl-phenyl,  483. 
Methylic,  Alcohol,  485. 
"       Hydride,  477. 
Miargyrite,  273. 
Mica,  356,  410. 
Microcosmic  Salt,  254. 
Millerite,  365. 
Mimetine,  348.  —  291. 
Minium,  347. 
Mispickel,  257,  378. 

Mixtures,  Distinction  from  Compounds,  10. 
Molasses,  522. 

Molecular  Condition  of  Gases,  17. 
"         Compounds,  132. 
"         Structure,  63,  76,  474,  476,  510, 

525. 
Molecular  Weight,  18. 

"  "        Determination  of,  126. 

Molecules,  Definition  of,  11. 

14         Constitution  of,  131. 


Tin 


INDEX. 


Molecnles,  Sum  of  Atomicities.,  122. 

Molybdate  of  Ammonia,  321. 

Molybdenite,  321. 

Molybdenum,  321. 

Molybdic  Anhydride,  321. 

Monatomic  Organic  Compounds,  485. 

Monazite,  441. 

Mono-acetine,  517. 

Monoclinic  System,  141. 

Monometric  System,  138. 

Mordants,  412,  442. 

Morphine,  249. 

Mortar,  341. 

Mosaic  Gold,  438. 

Mucic  Acid,  522. 

Multiple  Proportions,  Law  of,  10. 

Mundic,  388. 

Muriatic  Acid,  208. 

Myristic  Acid,  488. 

Mysorin,  330. 

N. 

Nagyagite,  321. 

Names  of  Binary  Compounds,  101. 
"      of  Elements,  101. 
"      of  Ternary  Compounds,  104. 
Napthaline,  483. 
Natrolite,  410,  456. 
Natural  Colors,  176. 
Naumannite,  320. 
Needle  Ore,  279. 
Niccoliferous  Smaltine,  365. 
Niccolous  Chloride,  366 
"         Cyanide.  —  371. 
"         Nitrate,  366. 
"         Sulphate,  366. 
Nickel,  365. 

"     and  Oxygen,  366. 
"      Glance,  365. 
"      Green,  365. 
"      Vitriol,  365. 
Nicotine,  249. 
Niobium,  296. 
Nitres,  215, 216. 
Nitric  Acid,  234.  -  236,  238, 239,  240, : 

317,  347. 

«      Anhydride,  236. 
"      Oxide,  238.  —  236. 
"     Peroxide,  237. 
Nitriles,  245. 
Nitro-benzol,  66,  482. 
Nitrogen,  233.  —  467. 
Nitrogen ,  Bromide  of,  250. 
"        Chloride  of,  250. 
"        Iodide  of,  250. 
"         Oxides  of,  234. 
Nitro-glycerine,  516. 
Nitrous  Acid,  236. 

Anhydride,  236. 
Oxide,  239,  240. 
Nomenclature,  100. 

"  Lavoiserian,  102. 

Notation,  33. 

0. 

Octahedrite,  430. 

CEnanthylic  Acid,  488. 

(Erstedite,  441. 

Ohm's  Law,  159. 

Oil  of  Bitter  Almonds,  501.  —  77. 

"     Garlic,  498. 

"    Meadow  Sweet,  504. 


Oil  of  Mustard,  498. 

"    Vitriol,  318. 

**    Winter  Green,  504, 
Oils,  Drying,  518. 

"     Essential,  481,  501. 
Olefiant  Gas,  479.  —  486. 

"    Series,  477,  479. 
Olefines,  479. 

"       Acid,  508. 
Oleic  Acid,  498. 
Oleines,  618. 
Oligoclase,  409,  456. 
Olivine,  356. 
Onofrite,  320. 
Onyx,  445. 
Oolite,  340. 
Opal,  Common.  444. 

"     Varieties,  445. 
Optical  Crystallography,  153. 
Orangeite,  441 
Organic  Chemistry,  473. 
"       Compounds,  473. 
Oriental  Amethyst,  Ruby,  and  Topaz.  408. 
Orpiment,  263. 
Orthite,  441. 

Orthoacids,  229,  232,  235,  252. 
Orthoclase,  409. 
Orthophosphoric  Acid,  252. 
Orthorhombic  System,  141. 
Osmic  Compounds,  420. 
Osmium,  420. 

Oxalic  Acid,  464,  505.  —  463. 
Oxamethane,  77,  244. 
Oxamic  Acid,  77,  244. 
Oxamide,  76,  243. 
Oxatyl,  465. 
Oxalic  Ether.  —  499. 
Oxidation,  301. 
Oxides,  Metallic,  82. 
Oxybutyric  Acid,  509. 
Oxygen,  300.  —  115, 125,  325. 
Oxygenated  Radicals,  484. 

u          Water,  202. 
Oxygen  Compounds,  301. 

"       Ratio,  451. 
Oxygen  Salts,  88. 
Ozone,  302. 
Ozonides,  303. 

P. 

Pachnolite,  408. 
Palladious  Nitrate,  424. 

"         Sulphate,  424. 
Palladium,  423. 
Palmitic  Acid,  488. 
Palmitines,  518. 
Paracyanogen ,  467. 
Paraffine,  477. 
Paralactic  Acid,  505,  508. 
Paraleucic  Acid,  508. 
Paraluminite,  409. 
Parentheses,  use  of,  34. 
Parisite,  364. 
Pearl  White,  276. 
Pelargonic  Acid,  488. 
Perchloric  Acid,  209. 
Perchromic  Acid,  405. 
Periclase,  354. 
Perissad  Elements,  201. 
Perissads,  59. 
Permanganic  Acid,  377. 


INDEX. 


Perofskite,  430. 
Petalite,  457. 
Petroleum,  458. 
Pewter,  434. 
Pharmacosederite,  379. 
Phenols,  501. 
Phenyl,  482. 

"       Alcohol,  502. 

"       Series,  477,  482,  501. 

"       Series,  Acids  of,  503. 
Phenylene,  483. 
Phoenicochroite,  406. 
Phosgene  Gas,  463.  —  508. 
Phosp  nines,  256. 
Phosphoric  Anhydride,  253.  —  86,  489. 

"         Chloride,  256.  —  63,77,316,509. 
"          Oxychloride,  257. 
"         Sulphochloride,  257. 
Phosphorite,  343. 
Phosphorous  Acid,  252,  257,  251. 
"  Anhydride,  252. 

"  Chloride,  256.  —  56,  493. 

"  Iodide,  —  497. 

Phosphorus,  250.  —  255,  493. 

Red,  251. 

Phosphuretted  Hydrogen,  255. 
Photography,  221. 
Physical  Properties  of  Matter,  10. 
Physics,  Definition  of,  3. 
Pickeringite,  409. 
Picric  Acid,  502. 
Pimelic  Acid,  512. 
Pink  Salt,  435. 
Pisanite,  379. 
Pitchblende,  293. 
Plaster  of  Paris,  342. 
Platinic  Compounds,  426. 
Platinous  Compounds,  427. 
Platinum,  425. 

Bases,  428. 
"         Sponge,  418. 
Plumbates,  348. 
Plumbic  Acetate,  347.  —  348,  349. 

"        Carbonate,  348. 

"        Chloride,  348.  —  349. 

"        Chromate,  403. 

"        Hydrates,  347. 

"        Nitrate,  347.  —  40,  237,  240,  466. 

«        Oxide,  346. 

"        Peroxide,  347.  —  305. 

"        Phosphate,  348. 

"        Sulphate,  348. 

"        Sulphide,  346. 

"        Sulphocarbonate,  466. 
Poles,  Positive  and  Negative,  165. 
Polybasite,  273. 
Polymerism,  134. 
Polymorphism,  133. 
Porcelain,  411. 
Porphyry,  411. 
Potassic  Aluminate,  216. 

"        Acetate.  —  478,  489,  493,  494. 

"        Bicarbonate,  216. 

"        Carbonate,  215.  —  467. 

"        Chlorate,  209.  —  300. 

"        Chloride,  216. 

*«        Chromate.  403.  —  300. 

"        Cobalticyanide,  370. 

"        Cyanate,  472. 

Cyanide,  468.  —  371,  469,  472,  513. 

"        Bichromate,  403.  —  399,  400. 

"       Dioxide,  216. 


Potassic  Ethylate,  —  472. 

"        Ferricyanide,  470.  —  469. 

"        Ferrocyanide,  469.  —463,  469. 

"        Fluoride,  —  232. 

"        Fluotantalate,  298. 

"  Hydrate,  216.  -  82,  84,  209,  357, 
376,  463,  472,  480,  499, 504,  510, 
513. 

"        Manganate,  376. 

«        Nitrate,  216.  —  238. 

"        Nitrite,  233. 

«        Oxalates,  464. 

"        Oxides,  216. 

u        Permanganate,  376.  —  377. 

u        Persulphide,  312. 

"        Pyroantimoniate,  269. 

"        Rutheniate,  419. 

"        Stannate,  436. 

"        Sulphate,  —  312. 

"        Sulphide,  —  312,  466. 

"        Sulphohydrate,  —  312,  487. 

"        Sulphocarbonate,  89.  —  466. 

«»        Tartrates,  217,  268. 

«        Tetroxide,216. 

"        Trichromate,  403. 
Potassio-ferrous  Sulphate,  319. 
Potassio-iridic  Chloride,  422. 
Potassio-iridous  Chloride,  422. 
Potassio-magnesic  Sulphate,  356. 
Potassio-osmic  Chloride,  421. 
Potassio-palladic  Chloride,  424. 
Potassio-rhodic  Chloride,  422. 

"  "       Sulphate,  422. 

Potassio-ruthenic  Chloride,  420. 
Potassio-stannous  Chloride,  435. 
Potassio-zirconic  Fluoride,  440. 
Potassium,  215.  —  465. 

«  Alum,  409,  413. 

Precipitate,  Definition  of,  36. 

"         How  represented,  35. 
"         When  formed,  37. 
Printing  Ink,  460. 
Propione,  495. 
Propionic  Acid,  488.  —  510. 

"        Anhydride,  493. 
Propionyl,  484. 
Propyl,  484. 
Propylene,  477. 
Propylic  Alcohol,  485. 

"       Glycerine,  518. 

"       Glycol,  505. 

"       Hydride,  477. 
Proustite,  220,  263. 
Prussian  Blue,  470. 
Prussiates  of  Potash,  469,  471. 
Prussic  Acid,  468. 
Psilomelane,  373. 
Puddling,  382. 
Purple  of  Cassius  225,  437. 
Pyrargyrite,  220,  273 
Pyroantimonic  Acid,  269. 
Pyrochlore,  296, 441. 
Pyrolusite,  373. 
Pyromorphite,  348,  291. 
Pyrope,  449. 

Pyrophosphoric  Acid,  252,  254. 
Pyrophyllite,  410. 
Pyrotartaric  Acid,  512. 
Pyroterbic  Acid,  498. 
Pyroxene,  457. 
Pyruvic  Acid,  611.  —  512. 

«•       Series,  611. 


INDEX. 


Q. 

Quantivalence,  55. 

"  of  Radicals,  59. 

Quartation,  223. 
Quartz,  444. 

"       Varieties,  445. 
Quick  Lime.  341. 
Quinine,  249. 

R. 

Radical,  Atomicity  of,  60,  132. 
"       Definition  of,  83. 
"       Substances,  38, 131. 
Radicals,  Acid,  83. 

Alcoholic,  73. 
"        Basic,  83. 

Compound,  38,  484. 
Raimondite,  379. 
Rammelsbergite,  365. 
Reaction,  Definition  of,  34. 
Realgar,  263. 
Red  Hematite,  378. 

"    Liquor,  414. 

"    Ochre,  378. 

"    Oxide  of  Zinc,  357. 
Reduction,  301. 
Remingtonite,  368. 
Rhodic  Salts,  421,  422. 
Rhodium,  421. 
Rhodonite,  373. 
Rhombohedron,  140. 
Rinman's  Green,  370, 
RoccelHc  Acid,  512. 
Rochelle  Salts,  214. 
Roman  Alum,  413. 
Rouge,  388. 
Rubidium,  217. 
Ruby,  408. 
Ruthenium,  419. 
Rutile,  430. 

S. 

Saccharic  Acid,  520. 

Saccharine  Bodies,  521. 

Sal  Ammoniac,  247. 

Saleratus,  214. 

Salicine,  523. 

Salicylic  Acid,  504.  —  502. 

Saligenine,  523. 

Sal  Prunelle,  216. 

Sal  Soda,  213. 

Salts,  86. 

"     Acid,  87, 105. 

"     Basic,  87,  105. 

"     Neutral,  87. 

"     Oxygen,  88. 

"     Sulphur,  89. 
Salt  of  Sorrel,  464. 
Sand,  445. 
Sandstone,  445. 
Saponification,  493,  515. 
Sapphire,  408. 
Sarcolite,  456,  457. 
Sartorite,  263. 
Scalenohedron,  140. 
Scapolite,  410. 
Scheele's  Green,  259. 
Scheelite,  322. 
Scheeltine,  322. 
Schorlomite,  379. 


Scolecite,  410. 
Scorodite,  379. 
Sebacic  Acid,  512. 
Selenic  Acid,  820. 
Selenite,  342. 
Selenium,  319. 
Senarmontite,  268. 
Serpentine,  356. 
Siderite,  378. 
Siegenite,  368. 
Silica,  444. 
Silicates,  446. 

"       Native,  448. 
1 '       of  Organic  Radicals ,  454. 
Siliceous  Sinter,  445. 
Silicic  Acid,  445.  —  86. 

"     Anhydride,  444. 

"     Bromide,  453. 

"     Chloride,  452.  —  61,  455. 

"     Ethers,  454. 

"     Ethide,  454. 

"     Fluoride,  451. 

"     Hydrates,  445. 

"     Hydride.  453. 

"     Hydrochloride,  454. 

•'     Iodide,  453. 

"     Methide,  454. 

"     Sulphide,  451. 
Silico-fluoric  Acid,  452. 
Silico-fluorides,  452. 
Silicon,  444. 
Silver,  220. 
Silver  Glance,  220. 
Slags,  380,  397,  447. 
Slate,  411. 
Smalt,  370. 
Smaltine,  368. 
Smithsonite,  357. 
Soap,  214,  216,  515. 


Soda-lime,  282. 
Sodic  Alum,  413. 

"    Aluminate,  414. 

"    Arsenite,  —  263. 

"    Bicarbonate,  214. 

"    Carbonate,  213.  —  214.  361. 

"    Chloride,  213.  —  208. 

"    Disulphate,  319.  —  87,  316. 

"    Ethide, —  496. 

"    Ethylate,  473,  492. 

"    Hydrate,  214.  — 82,84,350,412. 

"    Hyposulphite,  315. 

"    Methide,  —  489. 

"    Nitrate,  215.  —  234. 

"    Oxide,  215. 

•«    Peroxide,  215. 

"    Phosphate,  Common,  254.  — 361, 

"    Stannate,  436. 

"    Sulphates,  319.  —  35,  213. 

"    Sulphide,  312.  —  213. 

"    Sulphite,  315. 
Sodio-iridic  Chloride,  422. 
Sodio-platinic  Chloride,  426. 
Sodio-rhodic  Chloride,  422. 
Sodio-zirconic  Fluoride,  440. 
Sodium,  213.  —  481,  483,  492. 
Solder,  434. 
Solid  State,  11. 

"        "      Symbol  for,  35. 
Soluble  Glass,  445. 
Solution,  107. 

"        Curves  of,  108. 


INDEX. 


Solution,  Differs  from  Chem.  Change,  110. 
"        How  indicated,  36. 
"        of  Gases,  109. 
Spathic  Iron,  378. 
Specific  Gravity,  1. 

"         of  Vapors,  21. 
"       Heat,  16. 
Spectra  by  Absorption,  187. 

"      Chromatic,  176. 
Spectroscope,  176. 
Spectrum  Analysis,  181. 
Specular  Iron,  378. 
Speiss,  365. 
Spermaceti,  488. 
Sphaerosiderite,  378. 
Sphene,  430. 
Spiegeleisen,  381. 
Spinel,  408. 
Spodumene,  457. 
Stannates,  433. 
Stannic  Chloride,  435. 
"      Hydrate,  436.* 
«'      Oxide,  437. 
"      Sulphides,  437. 
Stannous  Chloride,  434.  —  208. 
"        Hydrate,  436. 
"        Oxide,  437. 
"        Oxychloride,  434. 
"        Sulphide,  437. 
Starch,  521. 
Stearic  Acid,  488. 
Stearine,  516. 
Steel,  382. 
Stephanite,  273. 
Stibines,  271. 
Stiboniums,  271. 
Stilbite,  410,  456. 
Stochiometry,  41. 

"  Rules  of,  42,  47,  48,  49. 

Strontianite,  344 
Strontic  Sulphate,  —  345. 
"       Sulphide,  -  345. 
Strontium,  344. 

"         Compounds  of,  344,  345. 
Suberic  Acid,  512. 
Substitution,  65. 
Succinamic  Acid,  244. 
Succinamide,  243.  —  245. 
Succinic  Acid,  92,  505,  612,  514. 

"        Series,  612. 
Succinyl,  484. 
Sucroses,  521.  —  522. 


Cane,  521. 
"        Fruit,  521. 
"        Gripe,  521.  —  35. 
"        of  Lead,  347. 
«        of  Milk,  521. 
Sulphantimonites,  273. 
Sulphates,  319. 
Sulphides,  309.  313. 
Sulphites,  314. 
Sulphoarseniatcs,  263. 
Sulphoaramites,  263. 
Sulpho-bismuthites,  279. 
Sulpho-carbonic  Acid,  466. 
Sulphocyanates,  473. 
Sulphohydric  Acid,  309. 
Sulphur,  308.  —  312,  314,  315,  316. 
"         Anhydrides,  263. 
"        Compounds  with  Oxygen,  313. 
"       Flowers  of,  309. 


Sulphur,  Liver  of,  312. 
Milk  of,  309. 
Suits,  89,  263. 

Sulphuretted  Hydrogen,  309 
Sulphuric  Acid,  316.  —  35,  36.  300,  314, 463, 

486,  491,  493. 

"      Nordhausen,  319.  —  316. 
"         Anhydride.  315.  —  35,  40,  86. 

Chloride,  319. 
Sulphurous  Acid,  314,  316. 

Anhydride,  313.  —  816. 
"          Chloride,  319. 
Sulphurylic  Chloride,  316. 
Sycocerylic  Alcohol,  60L 
Syepoorite,  368. 
Sylvanite,  321. 
Symbols,  33. 

"        Bracketed,  74. 
Empirical,  69. 
"        Graphic,  70. 
"        Rational,  69. 
Synaptase,  623. 
Synthesis,  9. 
Synthetical  Reaction,  35. 
Systems  of  Crystals,  138. 

T. 

Tabular  Spar,  343. 
Talc,  358. 
Tannic  Acid,  523. 
Tannine,  523. 
Tanning,  523. 
Tantalic  Acid,  298. 

"        Anhydride,  298. 
"        Chloride,  298. 
"       Fluoride,  298. 
Tantalite,  297. 
Tantalum,  297. 

"         Compounds  of,  298. 
Tartar  Emetic,  268. 
Tartaric  Acid,  519,  268.  —  217. 
Tartronic  Acid,  516. 
Telluric  Acid,  320. 
Tellurium,  319. 
Tellurous  Anhydride,  320. 
Temperature.  13. 
Tennantite,  263. 
Tension  of  Gases,  12. 
Tephroite,  373. 

Ternary  Compounds,  Names  of,  104. 
Test  Paper*,,  89. 
Tetradymite,  276. 
Tetragonal  System,  139. 
Tetrahedrite,  273,  274,  330. 
Tetratomic  Organic  Compounds,  619. 
Thallium,  222. 
Thenard's  Blue,  870. 
Theory  of  Exchanges,  189. 
Thiacetic  Acid,  —  77. 
Thomsenolite.  408. 
Thomsonite,  410. 
Thoric  Chloride,  441. 
Thoritv,  441. 
thorium,  441. 
Tin,  433. 

and  Alcohol  Radicals,  438.' 

Butter  of,  434. 

Pyrites,  433. 

Salts,  4-'M  —439. 

Stone,  433. 
Tincal,  230. 


INDEX. 


Titanic  Iron,  378. 
Titanium,  430. 

"         Compounds  of,  430,  431,  432. 
Titanous  Chloride,  430. 

"        Oxide,  432. 
Toluol.  477.  —  501. 
Toluylic  Acid,  503. 
Topaz,  409. 
Tourmaline,  228. 
Trachyte,  411. 
Travertine,  340. 
Triacetine,  517. 

Triatomic  Organic  Compounds,  515. 
Tribasic  Acids,  85,  465,  518. 
Tricarballylic  Acid,  518. 
Triclinic  System,  142. 
Trie  thy  line,  517. 
Trimetric  System,  141. 
Triphylite,  379. 
Triplite,  373. 
Tripoli,  445. 
Troilite,  378. 
Tufa,  340. 
Tungsten,  322. 

"          Compounds  of,  322. 
Tungstic  Acid,  322. 

"        Anhydride,  322. 
Turnbull's  Blue,  471. 
Turpeth  Mineral,  334. 
Turpentine,  Oil  of,  477,  481. 
Turquois,  409. 
Twin  Crystals,  150. 
Type  Metal,  265,  346. 
Types  Chemical,  62,  69. 
"     Condensed,  64. 
"     Mixed,  65. 

U. 

Ultramarine,  410. 
Unit  of  Atomic  Weight,  27. 
"      Current,  169. 
"      Electromotive  Force,  169. 
«'      Heat,  14. 
"      Molecular  Weight,  27. 
'«      Quantivalence,  201. 
"      Resistance,  169. 
"      Specific  Gravity,  2. 
«        Volume,  2. 
«'      Weight,  2. 
Unitary  Theory,  95, 132. 
Uranite,  293. 
Uranium,  293. 
Uranium  and  Oxygen,  295. 
Uranous  Chloride,  294. 
Uranyl,  293. 

Chloride,  293. 
Fluoride,  293. 
Hydrate,  293. 
Nitrate,  293. 
Potassic  Sulphate,  293. 
Urea,  243,  472,  473. 

V. 

Valentinite,  268. 
Valeramide,  245. 
Valerianic  Anhydride,  493. 
Valeric  Acid,  488. 
Valerolactic  Acid,  509. 
Valeryl,484. 


Valerylene,  477. 
Vanadates,  292. 
Vanadic  Anhydride,  292. 
Vanadinite,  291. 
Vanadium,  291. 

"         Nitride  of,  292. 

"         Oxides  of,  291. 
Vanadyl,  291. 

Vegetable  Kingdom,  Function  of,  525. 
Vermilion,  334. 
Vesuvianite,  456. 
Vinyl,  484. 

;      Alcohol,  497. 
"      Series,  497. 
Vitriols,  319.  329,  358,  379. 
Vivianite,  379. 
Voltaic  Battery,  161. 
Voltaite,  379. 
Volume,  1. 
Vulcanized  India  Rubber,  309. 

W. 

Wad,  373 
Water,  201.  —  80,  81,  202,  480. 

"      of  Crystallization,  94. 

"      Glass,  445 
Waves  of  Light,  176. 
Wavellite,  409. 
Weight,  1. 
White  Iron,  381. 

"      Lead,  348. 

"      Vitriol,  358. 
Witherite,  344. 
Wittichenite,  279. 
Wolfram,  322. 
Wollastonite,  457. 
Woody  Fibre,  521. 
Wulfenite,  321. 


X. 


Xanthosiderite,  378. 
Xylol,  477. 


Y. 


Yeast,  523. 
Yellow  Ochre,  378. 
Yenite,  379. 
Yttrium,  363. 

Z. 

Zaratite,  365. 
Zeolites,  410. 
Zinc,  357. —35,  387,  479. 

and  Alcohol  Radicals,  358. 
Butter  of,  358. 
Methide.  —  478,  496. 

Zincic  Carbonate,  358 361. 

Chloride,  358. 
Hydrate,  357. 
Oxide,  357.  —  361. 
Sulphate,  358.  —  54. 
Sulphide,  361. 
Zinkenite,  273. 
Zircon,  440. 
Zirconia,  440. 
Zirconium,  439. 

"         Compounds  of,  439,  440. 
Zoisite,  457. 


THE  HAMILTONIAN  SYSTEM  OF  LOGIC  AND 
METAPHYSICS. 


A   TREATISE    ON   LOGIC; 

Or,  The  Laws  of  Pure  Thought.  Comprising  both  the  Aristotelic  and 
Hamiltonian  Analyses  of  Logical  Forms,  and  some  Chapters  on 
Applied  Logic.  By  FRA.NCIS  BOWEN,  Alford  Professor  of  Moral 
Philosophy  in  Harvard  College.  Sixth  Thousand.  12mo.  Cloth. 
450  pp.  $  2.00. 


Extract  from  the  Preface. 

"  Among  English  authors,  after  Sir  William  Hamilton,  I  have  been  chiefly 
indebted  to  Prof.  Mansel ;  and  have  also  derived  much  help  from  Thompson's 
excellent '  Outlines  of  the  Laws  of  Thought » ;  but  the  work  would  not  have  been 
carried  on  in  the  same  spirit  in  which  my  predecessors  began  it,  if  I  had  not  ven- 
tured respectfully  to  dissent  from  some  of  their  doctrines,  and  even  to  present  some 
opinions  which  will  very  likely  be  found  to  have  no  other  merit  than  that  of  origi- 
nality  Throughout  the  work  I  have  kept  constantly  in  view  the  wants 

of  learners,  much  of  it  having  been  first  suggested  while  attempting  to  expound 
the  science  in  my  own  class-room." 


From  James  Walker,  D.  D.,  LL.D.,  late  President  of  Harvard  University. 

«« It  is,  so  far  as  I  am  able  to  judge,  singularly  complete,  and  yet  is  brought 
within  reasonable  limits.  As  an  English  text-book  in  this  department  of  philoso- 
phy I  have  seen  nothing  to  be  compared  with  h." 


From  E.  O.  Haven,  LL.D.,  late  President  of  Untverrity  ofMichiffan. 

"  I  have  examined  the  «  Treatise  on  Logic '  by  Prof.  Francis  Bowen  with  great 
care,  having,  indeed,  used  it  as  a  text-book,  and  have  found  it  the  most  thorough 
and  systematic  text-book  on  the  subject  with  which  I  am  acquainted.  I  think  it 
fully  supplies  the  purpose  for  which  it  was  written,  and  in  the  hands  of  a  good 
teacher,  it  furnishes  all  the  aid  that  he  or  his  class  will  need." 


From  Prof.  W.  D.  Wilson,  Hobart  Cottr.gr,  Geneva,  JV.  K. 

"  It  is,  in  my  opinion,  an  admirable  compend  of  what  is  now  taupht  as  Losn'c  ; 
presenting  with  great  clearness  and  skill  the  rival  systems  of  Aristotle  and  Ham- 
ilton, with  a  very  full  and  fair  exhibit  of  the  thoughts  and  opinions  of  all  others 
whose  writings  are  of  note  on  the  subject." 

2 


BOWEN'S  HAMILTON'S   METAPHYSICS. 

THE  METAPHYSICS  OF  SIR  WILLIAM  HAMILTON. 

Collected,  Arranged,  and  Abridged  for  the  Use  of  Colleges  and  Pri- 
vate Students.  By  FRANCIS  BOWEN,  A.  M.,  Alford  Professor 
of  Moral  Philosophy  in  Harvard  College.  Ninth  Thousand.  12mo. 
Cloth.  Price,  $2.00. 

The  publisher  takes  pleasure  in  stating  that  this  work  has  met  with  great  favor, 
and  haa  already  been  introduced  as  a  text-book  hi  all  the  principal  colleges  and 
institutions  of  learning  in  the  country. 

Extract  from  the  Editor's  Preface. 

"  As  any  course  of  instruction  in  the  Philosophy  of  Mind  at  the  present  day 
must  be  very  imperfect  which  does  not  comprise  a  tolerably  full  view  of  Hamilton's 
Metaphysics,  I  have  endeavored,  in  the  present  volume,  to  prepare  a  text-book 
which  should  contain,  in  his  own  language,  the  substance  of  all  that  he  has  written 
upon  the  subject.  For  this  purpose, .  the  '  Lectures  on  Metaphysics '  have  been 
taken  as  the  basis  of  the  work  ;  and  I  have  freely  abridged  them  by  striking  out 
the  repetitions  and  redundancies  in  which  they  abound,  and  omitting  also,  in  great 
part,  the  load  of  citations  and  references  that  they  contain,  as  these  are  of  inferior 
interest  except  to  a  student  of  the  history  of  philosophy,  or  as  marks  of  the  stu- 
pendous erudition  of  the  author." 


The  Rev.  Dr.  Walker,  late  President  of  Harvard  University,  in  a  note  to  the 
editor,  says  of  the  book  :  "  Having  examined  it  with  some  care,  I  cannot  refrain 
from  congratulating  you  on  the  success  of  the  undertaking.  You  have  given  the 
Metaphysics  of  Sir  William  Hamilton  in  his  own  words,  and  yet  in  a  form  admira- 
bly adapted  to  the  recitation-room,  and  also  to  private  students." 


Prof.  J.  Torrey,  University  of  Vermont. 

"  The  editor  has  left  scarcely  anything  to  be  desired.  The  work  presents  in  short 
compass  the  Philosophy  of  Sir  W.  Hamilton,  in  his  own  language,  more  completely 
and  satisfactorily  than  many  students  would  find  it  done  by  the  author  himself  in 
the  whole  series  of  his  voluminous  and  scattered  productions." 


From  the  North  American  Review. 

"  Mr.  Bowen's  eminence  as  a  scholar,  thinker,  and  writer  in  this  department,  his 
large  experience  as  a  teacher,  and  his  experimental  use  of  the  '  Lectures  '  as  a  text- 
book, might  have  given  the  assurance,  which  he  has  fully  verified,  that  so  delicate 
an  editorial  task  would  be  thoroughly,  faithfully,  and  successfully  performed.  We 
cannot  doubt  that  if  Sir  William  were  still  living,  the  volume  would  have  his  cor- 
dial imprimatur ;  ai/d  the  students  of  our  colleges  are  to  be  congratulated  that,  the 
labors  of  the  great  master  of  Metaphysical  Science  are  now  rendered  much  more 
availing  for  their  benefit,  than  they  were  made,  perhaps  than  they  could  have  been 
"s,  by  his  own  hand." 

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